Review: Gearbest Rustu/Kinfire K108S and Ultrafire C8

Firstly I want to thank GearBest for the opportunity to review these lights. ^^

So, why the joint review? Well, I must say, when I first saw the Kinfire K108 at GearBest I immediately liked the design. As I don't own any Ultrafire lights I wanted to see just what they can be like. The C8 is arguably one of the most popular budget models. When the lights arrived for me to peruse, a comparative review made perfect sense. You will soon see why.

Currently the Kinfire K108 is 18.71 USD, and the Ultrafire C8 is 8.44 USD. Both flashlights are designed to run on a single 18650 li-ion cell.

The Kinfire K108 shown left, Ultrafire C8 on the right:

The lights were sent in the usual bubble envelope; Ultrafire with no additional packaging. The Kinfire came in its own box and bubble wrap bag, which kept it nice and safe:

First thing I noticed about the Ultrafire C8. Maybe you can spot it?

It's only a sliver of swarf in between the fins. Not the end of the world.

The Kinfire has a Rustu logo, and model K108S on the bezel, so from now on I will refer to it as Rustu K108S. The colour is not black but a lovely grey. It might sound strange, but I do like the way this light feels in the hand. It has a nice weight to it. At 140g it is only 20g heavier than the C8.

Machining and anodization feel great. Not quite as nice as Convoy or Tank007 but noticably better quality than the Ultrafire, which is on par with other cheaper budget lights. There is a degree of 'you get what you pay for' here.

Now let's look a bit closer at the C8. Flecks of aluminium on the o-ring that seals the lens:

Some flaws in the otherwise smooth aluminium reflector. Note that these do not seem to cause any striking artifacts in beam profile:

Head disassembled:

Not perfect machining prior to anodize. O-ring also looks a little dry.

What's that? A curly piece!

Okay, enough. It's really nothing to take these out. They weren't pointing out in a way that could cause any injury.

Driver spring soldering is a bit grey:

The grip is just for show; body tube feels smooth. Threading is not squared, and single o-ring sealing only:

There is some silicone grease, but the threads were quite grey with old grease, so I will have to clean them with isopropyl alcohol and apply fresh grease.

A white plastic spacer holds the tailcap switch and boot in place. This plastic seems quite brittle; it won't hold up to many press-fits. There were already pieces breaking off in my fingers.

16mm LED star has no thermal paste:

The Rustu again:

It is almost perfect, except that the finned part of the head is a different shade to the bezel, body and tailcap. This is more noticable in photos than in the hand.

Bezel has a nice cutaway for the o-ring to fit snugly:

Bezel diameter is 44.5mm.

Non anti-reflective lens is quite thick:

More anodized threads. These fins feel great too. No sharp bits at all. I will not worry about handling this light in the winter with my knitted wool gloves.

The star is partly held in place by this retainer, which also serves to centre the reflector. Inspection of the retainer shows care has been taken to ensure perfect centering.

The reflector is very nice, only slight defects right at the LED opening, and near the inner edge of the bezel:

There is no spring at the head, so flat top cells will need magnets or similar to help make the circuit possible.

The Rustu tailcap has a brass button over the spring like in the C8:

The tube, with some lovely machining, and what could be accomodation for a second o-ring at the head end. Although it looks like it, these threads are not squared either.

The tube is just over 3mm thick.

A flaw in the anodize. It was going so well...

It is only cosmetic, but I hope Rustu/Kinfire take better care to sift these flaws out.

The glow-in-the-dark boot, proud of the tailcap:

This Rustu reflector, it has quite a weight to it. Such a contrast to the stock Ultrafire C8 reflector, which was so light I wasn't sure at first if it was aluminium or plastic.

Rustu reflector:

Yes, it really deserves another picture.

Rustu pill can only be inserted one way due to the flange. This extra mass aids thermal transfer to the head.

Ultrafire C8 pill is fully threaded and can be fitted either way:

Threaded diameter is the same.

Inside the heads (Rustu left, Ultrafire right):

Ultrafire C8 lens is rather thin and doesn't inspire much confidence. It is like the lens in my Goread CK-36, which broke easily.

There is a groove for the o-ring in the Ultrafire bezel, but either the o-ring is too small or the machining is just a bit off, so it doesn't sit nicely or stay put:

The Rustu tailcap disassembled. I like the tailcap 'pill' and switch PCB with spring (almost visible):

At 6mm the silicone boot is just a bit too long. Fortunately shorter boots can be sourced.

Ta-da! The Rustu 'legos' well with C8 parts (tailcap-body, body-head, pill-head). Okay, maybe a look inspired from Zara AW13 collection...

This is why o-ring seating is important to me. The seal in the Rustu is good. I do not like this gap on the Ultrafire lens (right). Maybe this is why the o-ring came fitted between the lens and reflector.

The Rustu driver is actually three mode (High, Medium, Strobe) rather than the five mode described on the product page. I am glad for the lack of additional modes (Low, SOS) but others might be disappointed by this.

I might be in a minority but I do not find a low mode on a light of this size that useful (certainly not as useful as a good Medium mode), whereas a strobe might be, for tactical distraction purpose. I don't want to cycle through too many modes to get to it either. Output-wise, this low mode would be better coming from a small pocket or keychain light, unless this was the only flashlight to hand.

There is mode memory, and a faint whine audible on Medium setting.

Just visible is a copper ring, to which the PCB was partially soldered to:

The Ultrafire C8 driver has next-mode memory, and five modes (High, Med, Low, Strobe, SOS). On the PCB is written "CX-5117-05", and there are many 3R0 resistors.

Both drivers have silicone wires to the LED.

Beam shots

Taken at 1m, 100 ISO.

Rustu R108S hotspot is more diffuse, quite ringy, with irregular corona:

Ultrafire C8 has a more controlled hotspot, and pleasing corona:


Measurements

Light output and current draw measurements. Both lights have XM-L T6 cool white emitters.

Rustu 108S draws a little more current, but is also brighter of the two.

For reference I have included additional measurements of Rustu 108S fitted with Nanjg 105c 6x7135 2100mA driver. It is visibly not quite as bright as the stock Rustu driver.

Light Mode Current A Lux 1m Lux 2m

Lux 3m

Candela 2m Candela 3m
Rustu R108S
High 2.3 22100 5150 2270 20600 20430
Med 0.33 5020 1220 564 4880 5076
Ultrafire C8

High 1.3 2800 1590 11200 14310
Med 0.83 2210 1114 8840 10026
Low 0.33 935 501 3740 4509
Rustu R108S with Nanjg 105c

High 2.1 19400 4570 2180 19000 19620
Med 0.65 6810 1710 773 6840 6957
Low 0.1 1127 272 123 1088 1107

Rustu R108S with Nanjg 105c

and anti-reflective lens

High 2.1 20400 4950 2310 19800 20790
Med 0.65 6410 1773 797 7092 7173
Low 0.1 1106 277 129 1108 1161

All lux measurements were taken after 30 seconds warm-up.

Conclusion

So, my overall impressions?

Ultrafire C8 is acceptable quality light for modding project, if prepared to change various parts. It may require some TLC before gifting. Some cosmetic issues prevent this from being anything other than a user/beater light. Quite surprising that the beam is nicer than the Rustu.

Rustu R108S light is very nice, let down only by a few cosmetic flaws and fuzzy beam. An aspiring shelf-queen, perhaps. It would be a great candidate for C8 modding (I already have some parts on order). The Rustu heats up quicker, and just feels better to use.

Thanks for reading! ^_^)シ

  • Updated review with new lux and candela readings, using anti-reflective lens.
  • Resized pics formatting from 800px to 500px wide and fixed broken links.

I have two coupons from GearBest for these lights. Coupons expire May 17th.

Kinfire K108

Coupon Code: GB5901

Coupon Price: 16.22 USD

Ultrafire C8

Coupon Code: GB8301

Coupon Price: 7.72 USD

Thanks for the reviews and coupons Chloe!

edit: I just see that you changed the prices.. they were mixed up...

Sorry, yes they were. ;_;

Thanks for the comparison Chloe, it provides more information than showing just the light reviewed.

Just a heads up: the Ultrafire C8 bare host, also at Fasttech, is a different one from the $8 one, build better and has a 'normal' C8 pill (the same that this Rustu has).

Thanks, djozz. What is the reflector like in the host kit? Do you think its beam is closer to the GB Ultrafire or Rustu profile?

It is a very ok smooth reflector, the beam looks like the Utrafire beam in the above review. I had a Convoy C8 host before, but it has stock a OP-reflector and a pill for 16mm led-boards, that is why I also tried the Ultrafire C8 host and was pleasantly surprised: standard C8 pill (although with space for a 19mm board, you have to file corners of a 20mm one a bit), smooth reflector and very good finish of the body.

The rustu beam might be caused by that centering ring, kinda tough to tell on mobile though.

You can definitely tell where the Ultrafire saved on their costs. :Sp

Great review Chloe!

Swap the C8’s reflector with the Rustu’s and you got the Rustu with good beam profile. :smiley:

The way I see these cheap Ultrafire C8s is I don’t really care how they perform stock, as long as it has solid pill and direct-drive driver I can turn it into beast. However the C8 in your review has a hollow pill, which would be a bottleneck for high performance mod. :frowning:

Wait, the C8 only draws 1.3A on high? What battery did you use? These cheap C8s usually give direct-drive on high mode. I have two $7 C8s from Aurabuy and both of their drivers are direct-drive on high. Using INR 20R battery gives me 4.6A+ of current draw.

I used a Sanyo 18650.

I tried the reflector and gasket from the C8 in the Rustu but the beam doesn’t look as nice. The hotspot seems to lose some definition. The LED opening in the reflector are not the same so need different gaskets (Rustu is 7mm diameter opening, C8 is 8.73mm).

Also annoying is the Rustu pill. It is too tall to fit in the C8 head (it isn’t milled deep enough like the Rustu head), so I have to use the Ultrafire pill. >.<

Excellent disassembly comparison and close up shots, thanks so much!!

:)

The c8's are really just a crapshoot . They are one of the most highly cloned lights out there so they have become the new 501B .. Ranging from well built ...to pure garbage .I'm not a big c-8 fan but the ones i have both have better bodies ... real knurling .real pills and probably much better anno.

This is one good thing about BLF members ...We all are looking for deals and can alert one another when the good ones show up cheap.

thanks for the review