Body: The battery tube has really thick walls. Much thicker than any other AA cell light. Of course this also means that its slightly heavier than most AA lights, and about 3/4cm to 1cm longer. There're four flat faces machined onto the tube. Other than than, the entire battery tube is a smooth cylindrical shape. Externally, the battery tube has a slimmer area towards the rear which helps when holding the light in a cigar style grip. The battery tube can accommodate both protected and unprotected 14500 cells without problems. As with the head, coating on the battery tube is just as well done. Very smooth and consistent. The threads between the battery tube and the tail cap are cut very smooth. I noticed that the more force you apply while screwing on the tail cap, the higher the chances of it getting cross-threaded. Otherwise, it screws on perfectly fine and smooth. The tail has a band of checkered textured knurling similar to that on its head. This provides adequate grip when unscrewing for battery changes. The clicking mechanism is on the stiff side with average travel and produces a positive clicking sound when engaged. The I25 can't tail stand since the rubber switch cap slightly sticks out the rear end of the tail end. The I25 is rated at IP-68 for water and dust resistance.

Bezel/Head:The head of the I15 houses a unique reflector cup which is half smooth and half textured, similar to earlier Olight models. The smooth surface area reflects a highly focused hot spot for optimal throw, while the textured surface area smoothens out any artifacts in the spill region of the beam profile. Its an innovative take on reflector design and produces a beam that is characteristic of Olight products. The emitter is just slightly off-center, but not by much. On the exterior, the head has a thin band of checkered knurling which provides some grip when you're twisting the head. The Type 3 hard anodized coating is smooth and consistent throughout, free of scratches or smudges. The threads on the head are not too thin or too thick. New to the I-series is an anti-roll feature in the form of a 6-sided hex shaped ring towards the rear end of the hear.

Output:Instead of having pre-defined brightness levels, the Olight I-series uses twists of the head to smoothly ramp its brightness level up or down. The direction of ramping alternates each time you loosen the head. To set the brightness level, simply tighten the head when you reach a particular brightness level during the ramping sequence. The I15 uses R2-binned LED's providing an output range of 6 to 205 lumens, taking about 2.5 seconds for a full ramp sequence either way. The digital current regulated circuit provides constant light output on all brightness levels with no signs of PWM flickering. You can also activate strobe and S.O.S. modes by half-pressing the switch within 2 seconds each time.

The color temperature on my sample is a neutral white, just slightly cool when compared to sunlight white. The beam profile has a spot which is well-focused and the spill beam is smooth without artifact thanks to its unique reflector design. There is a slight dark area right in the middle of the hotspot, but its not noticeable in practical use. The circuit in the I15 seems to have been tweaked for improved performance when running on an 14500 cell which produces a noticeable runtime improvement over the earlier T15.

Runtime is good for the intensity of light it outputs on the brightest level. Regulation is also maintained well on either AA or 14500 cells.

Switch: The switch is a rubber covered clickie and is fully recessed in the tailcap which allows the light to stand on end and be used as an electric candle. Despite the fact that the switch is recessed, it is very easy to use. Click on, click off. You can lock-out the switch by unscrewing the tailcap 1/2 turn. This will prevent accidental activation when packing the light in your backpack or luggage.

Batteries: For batteries, this light is approved by the manufacturer for use with one 14500 750mAh or one AA 2000mAh.

Accessories: Several accessories are included with the light.

Package

What I Liked:Very well built and finished. Provides a well-focused spot while still having a smooth, artifact-free spill beam. Maintains regulation nicely with AA or 3.7V 14500 cell while providing good output and runtime even on the brightest level.

What I Didn't Like: Slightly longer than most single AA powered lights.

Picky Little Things: None

Quick Facts Table:

Item Reviewed..........................	Olight I15 Infinitum
Review Date .............................	June 2009
Country of Origin ......................	China
Case Material ...........................	Anodized Type III aluminum
Case Features ..........................	Faceted sides around center, texture around tailcap, lanyard attachment
Case Access Type ....................	Unscrew Tailcap
Switch Type .............................	Clickie (reverse-type)
Reflector Type .........................	Smooth/Textured Aluminum
Lens Type ................................	Anti-Shattering AR-Coated Glass
Bulb Type .................................	Cree XR-E R2 LED
Beam Type ...............................	Tight Spot
Beam Characteristics ...............	Central smooth spot with slight corona and wide spillbeam
Throw (Lux) at 1m (click for description)	see table above
Overall Output (click for description)	see table above
Battery / Power Type................	1x 14500/ 1x AA
Battery Life (advertised) ...........	see table above
Battery Life (test results) ...........	see charts above
Environmental Protection .........	Beam diffuser, Nylon elastic holster, Spare GITD rubber button cap, Nylon wrist strap, Spare rubber o-rings
Weight (oz.) with batteries .......	1.87 oz. (need to convert to grams?) 2.593 oz with 1x 14500 AW 2.797 oz with 1* AA
Special Items of Note ...............	Many accessories included
Warranty ..................................	Limited lifetime
Retail Cost ................................	$50.95 US at time of review at Olights.com