Review: XENO S3A (XM-L U2 1B | 1 x 18650 / 2 x CR123A)

Bucking the recent trend of multi-emitter & multi-cell lights comes XENO's latest release, the S3A. It features an extremely small form factor for an 18650-sized light that is not much bigger in total volume than some AA-sized lights but with great output and significant runtime benefits.

• Could be the smallest 18650 flashlight in the world with a reverse clicky. 21.5mm x 111mm, 50g.
• Reliable encircled pocket clip
• 6 stage driver 3 brightness levels (High, medium, low) and 3 hidden modes (Strobe, Locator Beacon, SOS).
• Stainless steel switch guard (allows tail standing, can be used for self defense or to break glass)
• Availble with a Cree XM-L U2 1B Cool White, T6 Neutral White 3C, T4 7B Warm White.
• Powered by 1x 18650 or 2x CR123's.
• Precision polished Orange Peel reflector with double AR (anti-reflective) lens
• Linear current driver (no PWM) with built in reverse polarity proteciton. 24k gold plated springs.
• Mil-spec Type III Hard Anodized Aluminum. Color: Gun Grey.

•Light output (U2): 300lms
•Runtime: 2.5hrs High, 100hrs low
•Beam Distance: 65M
•Peak Beam Intensity: 1300cd
•Impact Reisstance: 1M
•Water Resistance: IPX-7, 1M.

The S3A comes with a black outer shell and a pretty nice off-white box w/magnetic flap:

Additional items included were:
• 2 spare O-rings (I only received one)
• 1 spare clicky switch
• 1 wrist strap
• Instructions / Warranty Information

I'm in the process of fleshing out the review so in the meanwhile, please watch a high-level summary of the design and features including UI coverage:

Maintaining a slim profile typically means sacrificing all extraneous design elements since it requires additional material to start with to be carved (and thus translates into extra bulk). While the SA3 adheres to this mantra, it does feature some milled work (albeit minimal) that prevents it from being completely a plain cylinder.

There is a SS bezel (that can be removed with the appropriate tool but surprisingly not w/the TW15) which secures a double-sided coated AR lens:

[NEW 6/20: There is a GITD o-ring right behind the lens but given its size, doesn't hold the lume long after it's charged:

A group of etchings on the head include the company name, logo and a symbol I had previously explained (in G10v2 review) to be a pictogram of a Tiger:

Just aft of the head is a groove for the clip to attach to and a thinner groove right after that . The clip is interesting in that rather than being the typical clip on style, there is an interlocking "dovetail" to keep it securely in place:

The clip also features an attachment point for the included wrist strap.
There are 5 evenly spaced "dumbell" shaped fluting milled in to the body of which one has the serial number etched within it:

There is one final groove right after this completing all the milled work of the head/body.

Having said that, given there was some space between the final groove on the body and the switch guard, the S3A may have been well served to have another clip groove milled so that the clip could be flipped and allow bezel down carry. Here's a photochop of what it potentially could have looked like:

The SS switch guard is crenelated allowing it to be used for strike purposes or glass breaking duties. The flat surfaces also allow for tailstanding:

There are five dimples running around the circumference and two holes that can be used as attachment points for the wrist strap or potentially to install a custom clip to allow the SA3 to be carried bezel down:

The rubber cover hides a reverse-clicky switch:

The reason this was selected over a forward-clicky is it shaved a few mm off of the total length. Every thought was put into making this light as compact as physically possible but yet retain a clicky switch.

The threads on the switch guard and body are square-cut and on the latter anodized thus allowing lockout with roughly 1/8 of a turn:

There are 24K gold plated springs at both ends of the light [NEW 6/11: and while both my shortest cell (AW IMR 1600 @ 65.2mm) and longest (XTAR 18700 @ 69.2mm) fit in the tube:

I wasn't able to completely tighten the tailcap w/the XTAR18700, thus they will NOT work w/the S3A:

I did confirm that my next longest cell (RL3100 @ 68.3mm) does fit.]

I've confirmed that the S3A's reverse polarity protection works without a hitch:

L: Battery reversed | R: correct polarity

[NEW 6/20: The S3A is just small enough to be used clipped to the bill of a cap and provided it's thick enough (like on the example I used), should hold in place reasonably well:

It is a little long and might end up being just mm's away from your forehead (depending on the cap in question):


L to R (same order for both sets of pics): RL 3100 | Sunwayman M11R | Fenix LD10 | Sunwayman V11R | XENO S3A | SureFire L4 | Surefire G2Z | Sunwayman T20C | XENO G10v2 | Prometheus Lights XM18-B

As can be seen above, the S3A is the smallest 18650-sized light in my collection so to help put things in perspective, I've taken a close-up vs. 1xAA lights below and SureFire L4 (2xCR123A):

L to R (same order for both sets of pics): RL 3100 | Sunwayman M11R | Fenix LD10 | Sunwayman V11R | XENO S3A | SureFire L4

Given the size is the main feature being touted, I've taken additional comparo shots to help you "size" it up:

I measured the diamter to be 21.4mm (.84in) and length @ 111mm (4.37in):

[NEW 6/20: The S3A fits well in my medium-sized hand, however given the tailcap guard, you'll need to position it to allow your thumb easy access to the button:

Despite the compactness of the S3A, the overall fit and finish is quite outstanding. The square cut threads are ultra smooth and the SS bezel was tightened without any gaps. While the lack of material may not convey the same perception of robustness as say the G10v2, it is still nontheless fairly tough. I had the S3A clipped to my belt that came loose and while getting out of the car, it fell from a height of about 1m onto concrete pavement but only suffered a minor ding to the side of the head and some light scratches/dents in both the bezel and tailcap:

(Note: The tailcap is not completely tightened in last two pics)

Despite this mishap, the S3A still functions flawlessly. Obviously, this wasn't an extreme impact test by any stretch of the imagination but I do feel the S3A should be able to shrug off a few knocks/drops.

[NEW 6/20: The anodizing matches across the entire light:

Nitpicking-wise though, there is some very minor ano missing from the inner corners of the machined fluting on the body:

As mentioned in my video, the engraving on the head while sharp has some minor blotchiness to it:

Although the serial number was fine.]

I was able to induce significant rattle with my smaller 18650's as the body has been designed to accomodate larger-sized cells:

However, this is really more a design decision than a fit & finish issue since most of the 18650 cells are neither 18mm in diam nor 65mm in length...

The S3A features three output levels: High, Low, Ultra Low (I really wish XENO would just stick with High, Med, Low since the Ultra Low at 20lms isn't exactly that). There is no memory so the light will always come on in High and then cycle through Med and then Low with each half-press (ie: not full click) of the reverse-clicky switch.

There are three hidden modes: Strobe, Locating Beacon & SOS that are accessed via three quick half-presses of the switch with the S3A on. Again, there is no memory in these modes so it will always come on in Strobe and then cycle through (with a half-press) the other modes sequentially.The only minor quirk w/the UI is that once it enters the hidden modes, you MUST shut off the light and wait 3 seconds before you can get back to standard output levels. It's strange they didn't allow the same three quick half-presses to exit hidden mode as it would've made so much sense. ]


Indoors (5m)
Celing bounce


Low (Med)

Ultra Low (Low)

For details of the above indoor shots and comparo vs. many other lights, please check Epic Indoor Shots Trilogy

The relevant battery stats are provided above each runtime graph along with:
- Voltage of the battery at the start and end of the test
- Current draw as taken right before the test
- Actual runtime using ANSI FL1 (first in HR and then in M so for the RL3100 read this as 3.4hrs OR 205min)
- NEW (as of May 2012): Lumens measured on PVC LMD @ 30 seconds
- Also for High, captured the temperature: ambient, the head at start and the max it reached (fan was used for all bats)

Using AW2600's I was able to slightly exceed (2.6hrs) the qouted run time of 2.5hrs. As can be seen, the S3A runs just about perfectly regulated before dropping off steeply, however at the end of this run, there was still usable light but I decided to stop it so as not to completely overdischarge the battery. Also of note is that it doesn't get all that hot hitting a max of 89F (32C).

[NEW 6/12: Completed runtime on H w/the RL3100 and as expected it yieled a longer runtime w/a trailing end as compared to the AW2600 with total ANSI runtime @ 3.4hrs. I continued to let it run to see if I could invoke the low voltage warning but was never able to get it to kick in so I finally stopped the testing at a littler over 4hrs. At this point, there was still very usable light of approximately 1lumen.

As for the overall lower output, I believe it has to do with the ambient temp which was higher than during the AW2600 run. Under the same temp, I actually expect the output to match for this regulated light. Will confirm later and post updates.]

[NEW 6/13: Completed runtime on H w/2 x Energizer CR123A's. Total ANSI runtime reached was just under 2hrs. I switched over to 400 range on my light meter once the output dropped to 0 on 4K range thus you see a jump in output around 160min. I then proceeded to let it run until the batteries were completely drained but finally had to give up just under 13.5 hrs into the testing.]

My first experience with XENO's products was with the G10v2. I was tremendously impressed by its build quality and the S3A has not disappointed in that regard. Its overall compact form and light weight may not convey the same feeling of robustness but the accidental drop "test" I incurred assures me that it should stand up to some heavy use.

The S3A has been a joy to EDC and really is at the cusp size-wise of what is EDC-able (for me). I relish the fact that I can get over 3hrs of ~340lms at near perfect regulation on High (using RL3100) if need be and much longer on the lower levels. I also like that there are additional hidden modes I can access even if I don't use them frequently.

The only minor points of annoyances would be the clip's positioning and the surprising amount of battery rattle. Hopefully a future version will feature a revised clip that would allow bezel-down carry. As for the rattle, as mentioned in my video, it's necessary since 18650 batteries can vary widely in their size. It's not a problem with the more recent and larger sized cells in this category.


  • outstanding build quality
  • extremely compact size offering great output and runtime
  • near perfect regulation
  • EDC-able 18650-sized light


  • awkwardly positioned clip that forces bezel up carry
  • copious battery rattle w/smaller sized 18650's and 2 x CR123A's
  • must shut light off completely to exit hidden modes
  • the Low and Ultra Low mode designations are really misnomers (they are actually Med and Low)
  • 18650 cells greater than 69mm in length will not fit


  • revised clip in future versions, perferably w/ability to be reversible for bezel down carry
  • anti-rattle sleeve for use w/CR123A's (although I don't use them personally I'm sure others who do will find it useful)
  • enthusiast version offering a little more oomph ;o)
  • slight bump in voltage range to accept 2 x LiFePO4's

Disclosure: XENO S3A provided by edcplus for review.


Hello. In your last picture of the 3 lights stacked up, what is the one on the bottom?



that it is a very nice light, but xeno's own e03 is significantly brighter. i'm sure runtime is great, but even if driven the same runtime would be better with the 18650. why underdrive this one so much?

Unless it was significantly discounted I wouldn't buy one because of the clip. Who the hell would clip a light lens out like that to it is exposed to dirt and scratches and the switch can get pressed in your pocket when you sit or something. Stupid design, IMO. :~

hows the low? its probably gonna be another xeno without a low enough low...

some critical points to consider:

- xeno's E03 is not known for perfect stabilization of brightness versus runtime, see quarks and zebralight: the E03 dims on HI-mode both on Eneloops and on 14500's.

- too long and heavy-ish for clipping to my trouser pockets. the 18700 XTAR cell alone weighs 48.1grams. i am not going to carry a 100g light in my pants, no way. (my Tank E09 with 10440 weighs 20grams!). the bezel-up pocket clip idea was exploited in 1xAA lamps for clipping to baseball hats and the E03, with a LD20 clip, works beautifully this way; weight and size suited the baseball hat well. however the S3A .. erh..

- the physical switch ("clicky") is the same el cheapo as known from the E03. the clicky will cause flickering at some point and then you either have to bath it in WD40 (or deoxit) or replace it with the spare el cheapo clicky. guess why Xeno has included a spare one in the accessories bag. it's not because Xeno is more generous than 4sevens with the packaged accessories. it's because the Xeno clicky is one of the cheapest and weakest point in the entire design.

- if you're a flashaholic then you probably like its optical design esthetics for 2 straightforward reasons: it's new, and it's a Xeno! and anything else doesnt bother you much and you are already about to pull the trigger no matter what because you love brand new lights especially if they are released by great flashlight brands. a true aficionado or collectionist you are, good for you, good for Xeno sales, i dont mind! [...] On the other hand i need to be honest and ask myself if i really do enjoy how a brand new torch looks .. and spontaneously i am thinking that the new Xeno doesnt match my taste; then again i dont like the optical designs of Balder's, Zebralight's, Sipik clones and so many other brands either, and hopefully the S3A meets the taste of many potential buyers! imho the E03 was kinda good-looking with an overall harmonic optical design. Btw, it's interesting why man finds something beautiful and why something isnt perceived as beautiful although only very very little differs, a subtlety maybe:

See for yourself...

This topic was covered in a BBC documentary (episode) about "What is beauty?". They found out that in general most people found something more beautiful when the item/object/subject/person/thing/etc was rather simple, symmetric, and had "perfect proportions" and thus produced harmonic looks in the eye of the beholder. When things got tangled, complex, complicated, asymmetric, disproportionate, distorted, the viewer had a hard time to call it "beautiful". No offense, I am not saying that i find the S3A ugly .. but i am saying that the left photo of the girl looks more beautiful (and harmonic and with better proportions) than the right photo duh.


@saypat - that's an old Fenix LD10 Q5, my 2nd/3rd LED light I believe.

@johnnymac - yeah, I'm never fond of bezel up carry for the very reasons you cited. I was clipping the light to the side of a pocket in my messenger bag last night and decided against it and instead left it bezel down within the pocket. On the plus side, one could clip this to the bill of a hat for hands free use but would've been great if one were able to reverse the clip.

@overclocker - the "Ultra Low" is quoted as being 20lms OTF. I'll have measurements up later tonight.

@cabfrank/kreisler - as with the G10v2, they have decided to drive the light moderately to increase runtime and prolong life of components, etc. With that said, these two lights run nearly perfectly regulated. The G10v2 does drop a little on High after turn-on but starting around 3 minutes (and provided there is sufficient cooling) will run perfectly regulated. I conducted a run of the S3A last night but due to 9999 row limitation of the Extech software logging, it got cut off but it runs perfectly regulated on High. I'll redo it tonight and post the graph.

As for the design, obviously beauty is in the eye of the beholder but I'd have to agree that the better proportions in the top pic is definitely more agreeable than the one on the bottom.

However, I suppose there is only so much you can do with a minimalistic compact form. Subjectively, I really like the design of the G10v2, but that has a substantial amount of extra material to it with which one could sculpt/mill with. The S3A is the polar opposite of that. The good thing is that XENO has been receptive to feedback and constantly upgrades their products.

Hey, you have a Zebralight SC60 you could put the Xeno next to and take a pic? I'm curious how they compare in size.

$60 is too expensive

You can get 4 x uniquefire 2100 for that price.

Sure it's nice but nothing special.

Johnny - sorry I don't have a SC60 but I did post up a side-by-side comparo with a SC30. Hope that helps.


5m indoor shots now added and review fleshed out some more. Also as a new procedure, I will be doing one bounce shot on max ahead of the beamshots to give a rough idea of total output. These will be added to the Epic indoor shots threads over time but for now, I have the S3A and G10v2 up.


Off topic but: for I second I thought you were going to say the bottom picture was more attractive... that's what I thot minus the huge forehead =P

have changed the photo and added a link in the post hehe..

BFL and off topic threads? -- that's rare ;)

Thanks for the nice pics + reviews but $60 is not my cup of tea!

Oh oops, I was looking from my mobile so I said bottom pic. I meant the pic on the right with the shifted eyes is more attractive – at least to me

Great review as usual, thanks very much! And that’s a very sweet flashlight.
Frontpage’d and Sticky’d.

Thanks for the review turbo!

It's a beautiful looking light!

Thx guys!

All, new material added along w/Fit & Finish & UI sections (search 6/11)

How good is stabilization on NCR18650A-based batteries? I’d guess just as flat up to ~2500mAh drained, then starts to gradually drop down?

I'll conduct that run tonight and post the results but yes, i'd expect it to be more or less as you've said.