The U2 reviewed here is the current revision which uses a SSC P4 instead of the original Luxeon V LED. The head section of the U2 is large, being about the same length as the entire battery tube. Despite this large size, it's relatively light-weight compared to the battery tube and tail cap put together and maintains a good balance when held in hand with batteries installed. The entire head is made up of four distinct sections. Right up the front is a bezel with shallow crenellations running along the rim. These allow light to shine through in case the light is accidentally left placed head-down. Behind the bezel sits an AR-coated, tempered Pyrex glass lens which provides good light transmission out the front, in addition to improved shock resistance. The reflector used has a fine textured surface finish which is perfectly finished upon visual inspection. The LED sits well-aligned at the bottom of the reflector cup, perhaps just a hair off-center. The mid-section is made up of two separate parts and has a series of shallow scallops machined around the mid-section. These are more of an aesthetic touch and do not serve as an anti-roll feature. Towards the rear is the control ring which serves as the interface with which the output levels are selected. The control ring has scallops and ridges which provide good grip. There are no detents or markings on the control ring to identify output selection. However, you can easily switch to either the lowest/highest output level by completely rotating the control ring in their respective directions where it comes to a stop. The control ring has a sufficient amount of resistance which prevents it from being accidentally rotated while in storage. Viewing from the rear, non of the electronics are exposed other than the "+" battery contact point. The bare aluminum threads on the head have slightly different surface finishing than those on the rest of the light, being somewhat matte rather than polished. A thick rubber o-ring sits behind the threads for water resistance.

The cylindrical battery tube has a band of knurling about 2.5cm wide going round its center portion. There're also three flat faces machined on where branding text are printed. A pocket clip comes attached on the battery tube by default. Although the wire clip looks somewhat flimsy as compared to other flat-style clips, it is very stiff and provides a very secure grip. This clip is also removable by removing the bracket holding it in place which is done by first removing the tail cap, and then simply sliding it out the rear end. The entire flashlight is finished in Type 3 anodizing from head to tail. Finish is smooth and consistent with no blemishes or shade mismatch which occasionally occurs in SureFire's with natural colored anodizing. Threads on both ends of the battery tube are well-machined mating well with both the head and tail cap. Note that threads on the U2 are of the regular variety and not the square-cut style as seen on some SureFire's such as the L1. The tail cap also has a band of knurling similar to that on the battery tube which provides good grip during battery changes. Housed inside the tail cap is a forward push button which mean that momentary activation is possible by half-pressing. The switching mechanism has average tension and travel, providing a slightly muted clicking sound when fully engaged. The rubber switch cap has a checkered texture and protrudes out slightly from the tail end so the light is not able to tail stand, though allows for more comfortable activation with a thumb.

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

The U2 Digital LumaMax, as its name implies, provides variable output levels which are controlled digitally by electronics in the head. The implementation of the control ring for output selection makes the light easily usable to the general user. No multiple clicking sequences are needed, you don't even need a manual to figure it out since it's pretty straight forward. While pointing the light towards a subject, rotating the control ring clockwise levels up, counter-clockwise levels down.

The beam profile produced by the U2 has a medium sized hotspot with a soft corona around its edge, tapering smoothly into the spill beam. Beam artifacts are completely absent thanks to the well-designed reflector. This review sample has a cool color temperature when compared to sunlight white.

Runtime performance is sort of a mixed bag with the U2. On the brightest Level 6, the light produced a moderately below average runtime falling just shy of 2 hours, although regulation is maintained well for most of this period. When compared to the other lower levels, runtime on Level 6 seems to be out of proportion as far as efficiency is concerned. Considering that Level 5 is about 30% of Level 6, the runtime produced is more than 6 times as long, and not about 3 times as one would expect. Looking further down the lower Level 4 which is about 10%, the runtimes become more proportionate lasting about 3 times times longer than Level 5. As the battery runs down to about 10% relative to each level, the output will start to pulse slowly about one every second to remind the user to replace them. Although not officially supported, the U2 can also be used with a 3.7V 17670 battery. Output on Level 6 will not be as bright with a 17670, but all other levels will be practically identical as with 2x CR123 batteries. The official SureFire web site advertises the U2 of outputting 100 lumens which is the original output rating of the original revision. No rating was specified for this current revision, but tests showed a peak of 187 lumens.

The Good - Excellent construction and finishing with a lifetime warranty. Control ring provides a simple multi-level user interface. Secure and well-designed clip. Very clean beam profile.

The Bad - Below average runtime on Level 6. Costs more than other lights with similar performance.

The Relative - Beam has a slightly cool color temperature. Uses a forward push button switch. Isn't able to tail stand. No detents or markings on control ring to indicate various output levels.

Head (front view).

Head (side view).

Head (rear view).

Battery tube (front view).

Head (side view).

Battery tube (rear view).

Tail cap (front view).

Tail cap (side view).

Tail cap (rear view).