[candle lamp]

The K18 is a 1xAAA light from Ultratac features a side switch, and compatible with 10440 Li-ion, Ni-MH and Alkaline battery. The packaging is the nice cardboard box. You can see the features and specifications on the front, side, and back of the packaging.
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The light come with removable pocket clip (attached), spare o-rings, key chain, user manual, and warranty card.
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Manufacturer Specifications from user manual :

• Max. output of 360 lumen
• Convenient one-handed operation
• Direct thermal path (DPT) copper MCPCB
• 3 light levels plus strobe
• Reverse polarity protection
• Compact size and light weight
• AR coating lens, 99% light transmittance
• Compatible with 10440 Li-ion battery
• Two-way clip provide more carrying options
• Battery option : 1xAAA Alkaline, Ni-MH, 10440 Li-ion battery


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The K18 looks small for the class. The anodizing is a light blue and no flaws on my sample. Labels are sharp and clear in bright white against the colored background. There are small patterned rectangles over the head and body tube.
The light has a built-in split-ring attachment point on the tail of the light, which prevents tailstanding. It also makes the light slightly taller. The light has no tail switch. Fit and finish look good.
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The light has 2 parts. The pocket clip works as a good anti-roll device as well.
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There is a patterned rectangles band on the head. The head has a clean looking cylindrical design with a electronic side switch. The side switch looks rubber, and it has a good feel to touch and has short travel, which produces a little clicking sound. The K18 switch is protruding and this may cause the risk of accidental activation. The light has reverse polarity protection to protect from incorrect battery installation (i.e., the K18 has a physical reverse polarity protection. You can see a very thin layer on the positive contact in the head).
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The light comes with a lightly textured reflector (OP) and uses a XP-G2 S2 emitter. Centering of the emitters was pretty good on my sample.
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The pocket clip looks sturdy and hold onto the light very securely. It is reversible, allowing both head-up or head-down.
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The battery tube is mostly covered in raised patterned rectangles. With the pocket clip attached, overall grip is acceptable, but not as grippy as actual knurling. The wall thickness of the body is 1.3mm. The light feels reasonably solid.
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The light uses a spring in the tailcap, like many lights in this class.
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The screw threads are triangular-cut of good quality. Threads are well machined, and anodized which allows the light to be locked-out. As supplied, threads are lubricated. Screw threads action is smooth with no cross-threading or squeaking in my sample.
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The K18 come with an included key chain. This large key chain can be quickly put or removed from the key-ring. While the key chain attachment point is quite useful, the attachment point prevents tailstanding.
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User Interface

There are two modes (i.e., general mode & strobe mode).

1) General mode
On-Off and output switching is controlled by the electronic side switch. Pressing and holding (0.5sec) the side switch will turn the light on, and another pressing and holding turns it off.

When on, a quick press and release (i.e., click) of the side switch will proceed Low -> Med. -> High, in repeating sequence. The light has mode memory, and remembers the last output level used when you turn the light off and back on.

2) Strobe mode
The “hidden” Strobe is accessed by double-clicking the switch when on. A single quick press and release (i.e., click) of the switch will return to the previous output level in general mode. The strobe has no memory.
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Standby Current Drain

Due to the electronic side switch interface, the K18 is drawing a small current when the light is fully connected. But I was not able to measure it, as I had blown the mA (including μA) current fuse in my DMM. So I was told by Ultratac that their test result is between 40~50μA when using 1.5V voltage power supply. For 1xNi-MH AAA (750mAh), that would translate into around 1.7~2 years before it would be fully drained. This is negligible, not much of a concern. But I would recommend you lock-out the light when not in use or to prevent accidential activation.
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From left to right, Panasonic Eneloop AAA (750mAh), Fenix E99 Ti (XP-E2), Rayus C01 (XP-G2 R5), Ultratac K18 (XP-G2 S2), Skillhunt Ramble-I (XP-E R2).
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Measured Dimensions

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The K18 is not a very small light, but good size to hold and use. You can use it as an EDC light. Overall build quality seems high.
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PWM

I can see PWM flicker on Low and Med. output when waving the light fast. But the flicker on both levels is not noticeable, you will not be annoyed in real life.
The K18 shows no sign of PWM on High. I hear a very small buzzing sound on Med. only when the light is very close to my ear.
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Runtime


The runtime to fall to 10% of its initial output from 30 seconds after the point the light is first turned on (i.e., based on ANSI FL-1) for High is as follows :

I don't have other runtime data in this class for comparison, but the results above says that efficiency on Ni-MH seems better than other battery sources. Unfortunately I was not able to test on 10440, as I don't have 10440 Li-ion cell.

The K18 drops down rapidly on Alkaline.
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Beamshot

1. White door beamshot (about 50cm from the white door) on max. output on 1xPanasonic Eneloop AAA (750mAh)
- ISO125, F/8.0, 1/25sec, Auto white balance


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- ISO125, F/8.0, 1/100sec, Auto white balance


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- ISO125, F/8.0, 1/800sec, Auto white balance


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- ISO125, F/8.0, 1/2000sec, Auto white balance'



The beam profile is pretty comparable to the others. It shows a bit wider hot spot than other lights. The overall beam profile is good. The beam has a cool tint, but warmer than I expected.
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2. 3.5m Indoor Beamshot on max. output on 1xPanasonic Eneloop AAA (750mAh)
- ISO125, F/2.8, 1/10sec, Auto white balance

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The above pictures make it look like all lights are not brighter than they actually are. So I took more pictures with 1/5sec condition which are much more close to real situation as below.
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- ISO125, F/2.8, 1/5sec, Auto white balance

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3. 7.0m Indoor Beamshot on max. output on 1xPanasonic Eneloop AAA (750mAh)
- ISO125, F/2.8, 1/10sec, Auto white balance

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The above pictures make it look like all lights are not brighter than they actually are. So I took more pictures with 1/5sec condition which are much more close to real situation as below.
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- ISO125, F/2.8, 1/5sec, Auto white balance

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Overall Impressions

• Build quality seems high
• The light can't tailstand
• Anti-roll indentations on the body
• Possibility of accidental activation from off, due to the slightly protruded electronic side switch
• Standby current drain (40~50uA) is inevitable, but not much of a concern
• Physical lockout function
• Physical reverse polarity protection function
• 10440 Li-ion is supported
• Mode memory for all output levels except Strobe
• True Moonlight mode is not available
• Use PWM for Lo, Med., but may not distract the user
• Overall beam tint is cool white, but warmer than expected

Ultratac K18 provided by Ultratac for review.