The head of the NiteCore Extreme makes up a large part of the entire light. Right up the front is a glass lens treated with NiteCore’s Dual-Coating process which results in improved light transmission as compared to plain glass. The bezel has a 3-point crenellation, the crenellations are thinner, but wider compared to those seen on some other lights. The bezel is adhered to the main head which houses the reflector, emitter and electronics. The reflector is textured evenly and well-aligned with the emitter. Externally the head has a band of knurling just below the bezel which helps with the mode changing done via head twists. Further down the head there’re 4 fins machined to help with thermal dissipation from the emitter. These fins also have 6 scallops cut into their sides for an aesthetic touch. The exterior of the head is well finished with smooth and consistent Type 3 anodizing in dark gray. The “E3” printed on the side of the head denotes the circuit used in the Extreme, and not the model name of the light itself and one might assume. Threads are well-machined, smooth and snug as well. I did not experience any grinding or cross-threading between the head and battery tube. Viewing the head from the rear you’ll be able to see the light module which appears to be made of brass. The “+” contact is spring loaded but not with just a bare spring, rather it uses a metal contact held in place by a white plastic ring. On a side note, the head actually fits on SureFire E-series bodies. Whichever body you decide to use, ensure that the input voltage does not exceed 4.2V.

The battery tube of the Extreme has lots of diamond textured knurling providing ample grip. There are also 2 raised ring machined onto both the front and rear ends of the body, these makes the Extreme really comfortable to hold in a cigar-style grip. The raised ring on the rear end has 2 flat faces machined onto it which act as an anti-roll feature. One of the flat faces is drilled with 2 holes with which you can screw on the included pocket clip. Speaking of the pocket clip, I found it to be way to lose because there is a significant gap between the clip and the battery tube. On the other hand, these would probably be good for people who prefer to clip their lights onto belts which are generally thicker than pocket. There’re also 6 holes machined on this rear raised ring which are primarily for designed purposes, though you can also use these to attach lanyards and such. The Extreme does not have a removable tail cap, the switch is house within the battery tube and held in place with a retaining ring. If you ever need to replace the switch, you’ll need to use a very narrow tipped pair of needle-nose pliers which would be able to fit into the notches on the retaining ring. The Extreme uses a forward push button switch which allows for momentary activation. It has a good tactile feel with average travel and provides good tactile feedback when clicked. NiteCore seems to have improved over the switch used in the initial batch of Defender Infinity which was slightly rough. The switch cap is made of relatively thick rubber and has a checkered texture, it sticks out the tail end of the light so the light won't be able to stand on its tail end. From my experience, NiteCore products come with very clean and dry threads and rubber o-rings. I would suggest that you apply some lubricant on at least the rubber o-rings to prevent them from wearing out too quickly.

If you're unfamiliar with any of the terms used in this review, click here for explanations on common flashlight related vocabulary.

The output from the Extreme is very bright, though this in turn affects the battery life. The beam profile is similar to that of the NiteCore Defender Infinity but is slightly narrower and had a sharply defined hotspot. The high crenellations at the bezel results in a spill beam which is slightly triangular. The hotspot is smooth and nicely focused, there isn't even the dark area in the middle which you see in some other lights. The spill beam does have the dark ring around the hotspot though. My sample of the Extreme has a slightly warm beam tint which is comfortable to the eyes. The Extreme uses a premium, Q5 bin emitter and is manufacturer rated to output a maximum of 190 lumens with a 3.0V CR123 cell and 200 lumens with a 3.7V 16340 cell.

The smooth brightness ramping sequence means you can set it to almost any level between its minimum and maximum levels. It seems very similar to LiteFlux's ramping sequence, but with a much simpler user interface (no more estimating 1/4 turns). Its levels are controlled via very high frequency PWM which is totally undetectable by human eyes, again similar to the LF series. Switching of modes is done by twisting its head. Listed below are the sequences for changing brightness levels and modes.

Initial Position: Tightened head.
Mode: Maximum brightness or strobe.
- Loosen and tighten within 0.5 seconds to switch between modes.
Mode state is saved even after turning off.

Initial Position: Loosened head.
Mode: User-defined brightness.
- Tighten and loosen within 0.5 seconds to ramp brightness up.
- Tighten and loosen again within 0.5 seconds to ramp brightness down.
Switch off to set and save user-defined brightness level.

Note: There seems to be a discrepancy with the runtime with CR123 cells as compared the those obtained by the manufacturer. Will be updated after doing another runtime on different cells.

The Good - Very good build quality, fit and finish is flawless. Comfortable size and weight with good ergonomics for various holding styles. Smooth brightness ramping with good brightness intensity.

The Bad - Clip has a wide gap between it and the body, so it doesn't fit securely on thin materials.

The Relative - Triangular spill beam profile with a slightly warm tint. Forward push button allows for momentary activation. Isn't able to tail stand. Head fits on SureFire E-series bodies.

Head (front view).

Head (side view).

Head (rear view).

Battery tube (front view).

Battery tube (side view).

Battery tube (rear view).

Battery tube (rear view with switch unscrewed).

Switch retaining ring (side view).