Review: Nitecore MT21A (XP-E2 R2 | 2 x AA)

Nitecore MT21A (XP-E2 R2 | 2 x AA)

This flashlight was provided for review by

Reviewer's Overall Rating: ★★★


Battery: 2 x AA (Alkaline, NiMH, Lithium primary)
Switch: Tail switch, Forward clicky
Modes: 6: Turbo, High, Med, Low, SOS, Strobe (in 2 groups)
LED Type: XP-E2 R2 (CW)
Lens: Glass, AR coated
Tailstands: No
Price Payed: Review sample. Retail price $30.99
Date Ordered: September 2013


  • Good build quality
  • Easy to use (UI is good both for beginners and experts!)
  • Throws pretty well for a 2xAA light
  • Current regulated -> No PWM on any mode
  • Good regulation & runtime
  • Well spaced modes (the low could be even lower for my taste though)
  • Good thermal characteristics - temperature raised only to maximum of 46°C during a 2h run indoors (ambient temp 23°C)
  • Unibody design in head
  • Lightweight
  • Flat bezel
  • AR-coated lens
  • Good lanyard (not the usual crap found in budget lights)
  • Comes in a nice retail box, lanyard included, good for gifting!


  • Doesn't tailstand (but on the other hand: the tail switch is very easy to use in this design)
  • Low mode could be lower
  • Not available as NW
  • No clip
  • Everything heavily glued -> not easy to mod

Features / Value: ★★★★

The light comes in a retail box which contains the light itself, lanyard, two extra O-rings, spare boot, warranty card, and a manual (in English).

This light has four well spaced, current regulated modes. Blinky modes are there, but only in User-Defined Mode group (see explanation below).

UI is good, divided in two mode groups which can be selected by tightening or loosening the head:

1) Turbo Mode (head tightened)

Simple "no-nonsense" functionality: Forward clicky switch allows you to have full power either momentarily (press lightly & keep pressed) or constantly (press until clicks, release). Note that there are no other modes in this group => No danger of changing modes accidentally!

Turbo mode has an automatic step-down feature: If the turbo mode is used over 3 minutes, the light steps down slightly (~30lm less, still higher than High mode) to prevent overheating. If you still want to continue with turbo, you can go back to turbo with turning light off and on again.

Please don't let the mode name mislead you: This is not a hyper super turbo which should not be used for a long time. In fact this is my most used mode with this light, giving constant 190lm OTF without overheating or any other problems.

2) User-Defined Mode (head loosened)

Five modes, with working memory. Just press the forward clicky tail switch and the light always starts on the last mode used.

To change modes, turn light off and on in 2s period. Modes are changed in the following order: High, Med, Low, SOS, Strobe.

I really like this UI, since it gives me the best of both worlds: Easy access to full power and many lower (and blinky) modes with memory. You can think this light as a two mode light: Just tighten the head and select between those two modes. My preferred setup is "Turbo + Low", but for example security guards might find "Turbo + Strobe" very useful.

Similar kind of UI has been seen in 4sevens Quark X AA2 Tactical, but Nitecore has a great advantage: Configuring the User-Defined Mode is easy. Almost as easy as using a normal 5-mode light, but with forward clicky.

Or when loaning this light to a novice user, just tighten the head and say that it's one mode light. ;)

Value for money: Good!

Design / Build Quality: ★★★

Design is very simple, nice, and easy for eyes. Reminds me of Fenix E21, but is significantly thinner and lighter.

The anodization is very good overall. A bit glossier than E21, but doesn't have a "painted" feeling. Texts are crisp and clear. Head doesn't have knurling, but it didn't bother me, not even when changing between modes.

Bezel is flat and emitter well centered. Just like I want 'em!

Lens is glass and clearly AR-coated:

Let's see some details..

Tailcap taken away. Here we can see the well lubed, anodized, square threads and thick O-ring. Tailcap has a hole for attaching the lanyard.

The spring at tailcap is thick and of good quality. The switch is kept in the place with a retaining ring and a lot of locktite! I didn't get it open with any available tools. It's a bit strange since there was even a spare boot included..

Head taken away. Threads are not anodized on this side, but still well lubed and of good quality. Note also the thick walls at this part of light.

Three basic parts of the light: Body, head, and tailcap.

Another pic showing them in the right order: :)

That is as far as an ordinary user should disassemble the light.

..but I had to open the head to see how the reflector design & thermal management are in this light..

After trying several methods, and quite much time, I finally managed to open the head, and this is what I found.. Lots of red locktite!

After I got over that shock, I saw a pretty sight: No pill, but uni-body design with thick platform under the star. Star was mounted with good amount of thermal paste (not too much) and the ground path to driver was secured with third lead screwed and soldered to the body.

Other side of the head reveals the reason for third lead: The driver is glued in!! [I didn't want to break it, at least not before beamshots & measurements, so it is still intact]

Note also the reflector. It's made of aluminum and has side walls which keep it in place & well centered.

The included lanyard is long, round-shaped & thicker than normal, and has tightening device in between. It must be one of the best lanyards I have seen in budget lights!

Some measurements:

Length: 157mm (including the protruding tail switch, 153mm body only)

Head diameter: 25.5mm

Body diameter: 18.7mm

Tail diameter: 21.5mm

Tailcap protrusion: 4.0mm

Lens diameter: 23.0mm

Lens thickness: 1.5mm

Reflector diameter: 22.7mm (inner dia: 19.9mm)

Reflector depth: 18.1mm

Weight: 132g with 2 cells (= ready to use), 70g without (compared to E21: 150g/98g)

..and here's some pictures confirming the measurements:

Compared to Fenix E21: (Note how much thinner MT21A is!)

And the bottom line in the quality: Nothing to complain. Except the non-moddability due extensive use of locktite (shouldn't bother "normal" users).

Battery Life: ★★★★

Good! Two batteries and good mode arrangement with pretty low low will allow very long runtimes.

I measured the tailcap current and got results of 2.0A on Turbo, 0.53A on High, 0.21A on Med and 0.04A on low.

This would give only about 1h runtime on Turbo, but the step down helps a lot, enhancing the runtime nearer to 2h on Turbo.

Calculated runtimes for other modes are: 5h on High, 12h on Med, and over 60h on low!

I would like to see yet another low-low mode with around 1lm (or 0.005A), which would give us around 500h runtime.

Light Output: ★★★

Runtime graph: (Eneloop XX 2500mAh cells)

The first almost three minutes are on turbo, rest of the graph on stepped down level (still higher than high). This runtime test was done indoors, with ambient temperature of 23°C, without any additional cooling. This light seems to be well regulated and handles the heat very well.

This light has kind of a low voltage warning (light flickering with very low level), which kicked in at about 1:51.

Let's try again, for first 10 minutes, forcing the turbo on:

The initial light output on Turbo was 256lm and ANSI-readings (OTF, after 30s) were:

- 224lm on Turbo

- 190lm on stepped down Turbo

- 127lm on High

- 65lm on Med

- 14lm on Low

Those measurements do match pretty well the advertised values, except on the turbo, where Nitecore might have taken the initial value(?)

Measured throw is 11kcd / 200m (compared to E21: 6kcd / 150m)

White wall beamshots (1/100s, f/5, ISO80, WB: Daylight)

Turbo (vs. E21 High)

High (vs. E21 High)

Med (vs. E21 Low)

Low (vs. E21 Low)

Turbo (vs. E21 High) again with reduced exposure (1/400s):

Beam patterns:

Beam angles:

Outdoor beamshots:

Coming soon.

Summary: ★★★★

Well designed & built AA-powered light that can be safely given to anyone (even to my mother!). No worries about Li-Ion cells, no overheating (even on Turbo mode), enough power & throw, easy UI, ... What's not to love? [Glue?]

Verdict: Recommended! [Not recommended for modders though]

The End (pun intended):

Thanks for reading & watching. Hope you enjoyed the review!

Thanks for the review the. Looks like a real nice little light. The more I think about all this glueing (yes I’m a bit slow) is for warranty. If its glued together you cant get sticky fingers in the to play havoc.

Very nice review, thanks.

I like the light but would also like to see a neutral white version, preferably around 4000K. Or else no loctite would be fine as well.

Good news: The banggood representative liked my review so much that he decided to give out ten (10) Nitecore MT21As for only $26 with coupon code bgf108.

So.. Only ten.. Be quick! :)

Great review on a nice light! Thanks 8)

Smaller emitters such as XP-E2 are ideal for 2xAA lights intended for outdoor use, IMO. A 2xAA light won’t ever be a lumen powerhouse so I’ll take some extra reach over flood when outside the house.

Yes i was quick :wink:

1. MT21A uses XP-E2 R2 emitter.
2. About beamshots - Nitecore is on the left, am I correct?

1. Oops. Thanks for noticing! I stand corrected. Fixed in the review.

2. Yes, Nitecore on the left

11klux/1m from thin 2xAA light, I’m impressed. I don’t like the sequence of modes with head loosened - it should be low-med-high instead of high-hed-low. Hidden strobe and SOS would be nice as well.

Thanks for the great review. Great price for so many modes :slight_smile:

Another fine review , sir .

Thanks .

Great review on a very interesting light thank you for doing this.

Good work and great review!

I’m glad I wasn’t the only one who couldn’t get the tailcap apart. I was trying to install a new GITD tail button and I said the same thing in the other thread about this light. Why do they even include an extra tailcap button when the tailcap is just about impossible to get apart? GR-R-R-R! :slight_smile:

Nice light though and I’m glad I got one.

Thank you for the review, I use the earlier version, a Nitecore MT2A as my EDC and like you suggested I use the Turbo and Strobe modes by loosening and tightening the head, not a security guard though, just self defence.
I find mine to be easy to use and carry, I would buy another, or the MT21A, if mine got lost.

Is there any difference between

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h t t p:// (the aff ID link you posted)


Or is there any difference between

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i was a shill before, not anymore. a peom by kriesl ©2013

Personally, I don't like affiliate links, but check out reply #36 (sb56637's post) in this thread:

i did not know that these were affiliate links.

well i was not sure about them.

the links were not declared as affiliate links.

at least fran82 and Buwuve state clearly that the links they are posting are affiliate links.

Saved for posterity.

Thank you for taking the time to review the light for us, very much appreciated!

I just got mine in (actually two :slight_smile: ) and I noticed the strobe mode alternates in frequency every two seconds; a rapid strobe at 21.85Hz and a slower strobe at 12.14Hz. Might be useful to include this info in your review.

The two I got do differ slighly in output (there will always be sample variance) and the step-down timer is different as well. Here are some LBL numbers (lightbox lumens) with my two samples.

MT21A #1
Turbo - 276.1 (0s) / 249.6 (30s) / 201.7 (142s) LBL
High - 124.4 (30s) LBL
Med - 57 (30s) LBL
Low - 9.3 (30s) LBL

MT21A #2
Turbo - 239.2 (0s) / 217.6 (30s) / 176.7 (148s) LBL
High - 122.6 (30s) LBL
Med - 68.9 (30s) LBL
Low - 14 (30s) LBL

Overall in the end I’m pleasantly suprised by this light. Good output and great throw for the 2 X AA format. I wish there was a stainless steel bezel to protect the lens, but for the price I paid I really can’t complain at all.