[Review] ULTRATAC K18 (XP-G2 S2, 1x AAA / 1x 10440)




Battery: 1x AAA / 1× 10440
Modes: 3 (+ hidden Strobe)
Switch: Digital, head.
Date: November 2015


Today we have again a new brand under scrutiny: UltraTac, and his new small flashlight keychain, the K18.
UltraTac is a relatively young brand, founded in 2014 by three Flashaholics, and has a team of people, some of them professional engineers with over six years’ experience in different brands such as Olight, Fenix or Lumintop.
As I’ve been told by the manufacturer, the K18 we will review today began to take shape in 2014, and after 7 redesigns to round up the model, the first units built have been testing during the last three months before the official launch a few weeks ago.

Initially the flashlight is available in three anodizing colors: Blue, Red and Black, but I’ve been told that soon we will see some more sophisticated finishes such as stainless steel, brass, nickel and golden plating.

The presentation of the flashlight is very good. The packaging consists of a small telescopic box inside a sleeve where we can see each and every one of the main features of the model, with color printing.

Inside the box, along with the small flashlight, we found a small plastic bag with a pair of spare replacement o-rings, a small aluminum carabiner and a brief but concise manual, and a small warranty card.

The Flashlight shows excellent finish. My unit is anodized in black, with a bit glossy touch, though fairly discreet. The main features of this Flashlight are quite compact finish with a rectangular knurling both in its central region and around the flashlight head.

Its measurements and weight are fairly contained, thanks to its side switch on the head is extremely easy and convenient to use.

The optics of the small UltraTac K18 consists of an XP-G2 S2, with its small OP reflector. The LED emitter is reasonably well centered in my unit. The optical assembly is topped with a glass lens with AR treatment on a flat bezel. The optical finish is clean and well resolved.

Right in the center of the head knurling track we have the greatest atraction of this small flashlight: a digital switch by which we will completely control all the user interface of this flashlight. This switch is covered by a silicone button, were we can read the word “MODE” extruded therein.

The switch protrudes just 0.9mm from the flashlight profile, but it’s simple and easy to locate by touch. This switch also helps keeping the flashlight from rolling if placed on a flat surface.

We have two engravings placed on the head: we have right under the switch brand and model letterings, and on the opposite side we find a unique serial number that identifies the flashlight.

Inside we have direct view of the driver and its container, which seems to be machined from brass and seems to be easy to remove for possible upgrades or LED emitter replacements.

Flashlight threads are anodized and feature the classic triangular cut. They arrive correctly lubricated and clean. The play between the two threads is minimal, and one can feel perfectly as the o-ring contacts the inner walls of the flashlight when screwing both parts.

Inside the tube are a spring located at the bottom of the battery housing, which has a fairly high tension. The space for the battery, even having quite strong tension spring is generous and allows use protected 10440 batteries, which are usually always one or more millimeters longer than unprotected or usual AAA’s.
The flashlight body is almost completely covered by a rectangular knurling, and has two flat tracks to secure the pocket clip in two directions.

The tail of the flashlight features a large opening with a pre-installed split-ring. This anchor point has a rounded finish, so the torch cannot be placed tailstanding.

Finally, the manufacturer has included with this sample a small silicone diffuser, which is sold separately and which can turn the flashlight in a small portable lamp. The diffuser is very similar (or identical) to what we can be find in the Maratac AAA series, and is compatible with almost any AAA flashlight in the market.

A curious detail is that the diffuser is made of a material that glows in the dark, so that after turning off the flashlight the diffuser cap will continue glowing for several hours, making this extremely easy to locate in the dark.


Although the flashlight features a “new” switch style in its segment, the operation is very similar to what we are used to in other larger flashlights employing similar digital switches in the head.

  • On and off: To turn on the flashlight, we must press the digital switch by half a second, and repeat the operation if we want to turn off the flashlight.

  • Changing Modes: With the flashlight on, just make a simple click on the digital switch to change modes, alternating between three intensities in ascending order: L-> M-> H

  • Memory: The K18 has mode memory function. This will remember the last used mode used prior to turn off, and will turn on in this mode in the next activation. The memory is retained even when the battery is removed off the flashlight.

  • Strobe Mode: As in other small AAA flashlights, strobe is a hidden mode, which can be accessed by a quick double click with the flashlight on. The frequency of the strobe is not too high, so it will be very useful as a locator/waring signaling.

  • Block-out: Having the switch quite exposed, fortunately we block out the flashlight when we don’t plan to use it to avoid unwanted involuntary activations. To do this, and thanks to its anodized threads, simply rotate a quarter turn of the head thread. Doing this will also stop the (always present in flashlights with a digital / electronic switch) parasitic consumption/standby current. After measuring the standby current necessary to maintain in “alive mode” the circuit of the flashlight, I have around 75uA (0.075mA) with an eneloop ( 1.4V) and around 18uA (0.018mA) with a 10440 ( 4.1V). Making a rough calculation, the K18 will completely drain by standby current a 800mAh AAA battery in 14 months, and a 320mAh 10440 in two years, of course regardless in both calculations of the self-discharge rate of the batteries themselves.

(All measurements are taken following the ANSI NEMA FL1 procedure, taking as value the highest reading of between 30 and 120 seconds after activation. More details here.)

The distribution of modes is fairly balanced and proportional between the two battery types. We have certain discrepancies between specified by the manufacturer and what the integrating sphere collects, although in general the K18 shows a concordance “in the usual” given the peculiarities of the calibration of our device.

The use of an XP-G2 in a AAA flashlight is nothing new, although it is rare to see a working flashlight, officially, both AAA’s as 10440’s. The K18 is one of those rare exceptions, and it is time to see how flashlight behaves in the usual test of time vs runtime, in which we will see how is the regulation of the flashlight to detail.

With an AAA eneloop and the High mode we have a really good performance with output that exceeds slightly the 110LM at activation, although the torch seems to maintain a constant slightly decrease till approximate 50 minutes, where the voltage is insufficient drops to much lower output, without turning completely off, surpassing the 70 minutes.

With a 10440 have a similar regulation for the same High mode, though far more powerful and therefore for less time. With nearly 400LM the activation, the torch begins its particular descent to reach 12 minutes (approx.), where the decline is becoming more pronounced, reaching more than 20 minutes on. In the Medium mode, we have a much more linear regulation, which provides a more or less constant output by just over 90 minutes.

Comparing AAA eneloop High mode curve thus the Medium mode obtained with 10440, we will see how the K18 is much more efficient with the small Li-Ion cell.

Comparing the curves, we see how the K18 is something above the Olight I3S and Bronte RA01 as referred to runtime, leaving only below the D25AAA Mini as a regulated output is concerned.

With 10440, we see again the K18 gets a great result, as one of the flashlights (of which I have seen) that work best with this battery, keeping the curve quite higher than most competitors, although accusing this in total runtime.
Finally, K18 modes are achieved by PWM, although it’s a quite high frequency so it is hardly noticeable, even by shaking the flashlight at its lowest output in front of a mirror.


The beam profile of this flashlight is virtually identical to what we find in many other AAA flashlights that use a combination of OP reflector with XP-G2 emitter, so there is not much to say here as this is one of the most widespread combinations in this segment of small flashlights.

We have a hotspot of medium-large size that blends smoothly and fairly evenly around the spill light. Thanks to the small size of the reflector beam along the edges of the illuminated area is not sharp, and instead we have a pretty nice soft gradient.

The tint used is cold white, and though the bin XP-G2 is quite high, S2, we have no clear dominant color.


Again a newcomer offers, almost at first, a truly well-rounded and interesting product that will make for sure up the colors to more than one already established manufacturer. UltraTac has been able to see a hole in the already saturated market niche of small AAA Flashlights for keyrings, incorporating a new concept that, although we have already seen many times in other segments, so far afaik no one had been reproduced in flashlights of this size. A digital switch in the head of a flashlight always makes it more comfortable to use, especially if it is a short flashlight that cannot be hold like a tactical one. It also prevents the action of twisty in compact flashlights, which we have to finish threading his head screwed on and make quick-unscrewed to change modes. The user interface is easy and really intuitive, for its similarity to other flashlights of similar performance and design.

Fenix LD01 · Ultratac K18 · Nitecore T2s · Tank007 E09 · Eagtac D25AAA Mini · Olight i3S EOS · Nextorch K10

Negatives: I have only one real complaint about the K18, and as it cannot be otherwise relates to the design of the tail end. The design of the tail, with that rounded machining anchor point prevents us from placing the flashlight in tailstanding, and considering that there is a cylindrical mini-diffuser, UltraTac is missing a fantastic opportunity for providing the small K18 an extremely practical function: A tailstanding lamp.

Positives: Starting with mechanical finish, following with the round and friendly user interface, its performance actually above the most popular AAA flashlights or its compatibility with AAA batteries (primary, rechargeable) and 10440 (rechargeable), I think UltraTac has done a great job with their first AAA light, comparable to any other already established brand. Instead of having persecuted astronomical numbers, for example using an XP-L, they have adhered to the well-known XP-G2, we know from experience that offers a balanced beam really useful for this kind of support flashlight such as that brought in our keyring or hanging from your backpack’s zipper. The user interface is similar to that found in other larger flashlights with a switch of the same characteristics, so we get to it in a matter of seconds without having to go through a learning process. If you want a powerful, compact and one hand easy to use flashlight, working both with AAA’s & 10440, the K18 can be your answer.

*UltraTac K18 review sample provided by manufacturer for Test & Review.