The LD01 has a smooth bezel, a rubber o-ring sits between the bezel and lens which provides a moisture seal. The lens used in the LD01 is made of toughened AR coated glass, as with all Fenix lights. The LD01 uses a smooth aluminum reflector which is tiny which keeps the tubular form factor of an AAA light. The finish on the reflector is well done, nice polished and smooth. The LED sitting at the bottom of the reflector is slightly off-center as can be seen from the image to the right. The entire head of the LD01 is made of two pieces of stainless steel adhered together. The exterior of the head is pretty simple with only a band of knurling present. This helps with grip and useful in a twist activated light such as this.

The LD01 has a polished stainless steel finish throughout, however it's not a mirror finish as shown in the manufacturers official product pictures. There are some minor marks on the surface finish which seems like a step down compared to the regular anodized finish of other aluminum Fenix lights. The plus side to this is that scratches on the finish won't be as obvious. The threads on the head and battery tube mate together very well. They're well machined and do not grind or cross-thread, there should be no problem switching modes via head twists single-handedly. An o-ring sits just behind the threads on the battery tube for moisture seal as well. There is a spring at the bottom of the battery tube, this means that the battery will not rattle when the head of the LD01 is loosened in the off position. Externally the battery tube has a hex shape cross section with six flat faces. These flat faces do well in providing grip with such a small light. Right at the rear end of the battery tube are two lanyard holes. The LD01 is also able to tail stand without problems.

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

The LD01 has 3 output modes in the following order:

Off > Medium (27 lumens) > Low (10 lumens) > High (80 lumens)

The small reflector does an amazing job of producing a focused from considering it comes in such a small form factor. The hot spot has a slightly darker center region. There's a soft corona just outside the hotspot, which itself is surrounded by a slightly darker ring. The corona is slightly lopsided due to the off-center reflector.The beam's color temperature on my sample is a very nice neutral white, leaning slightly towards the cool side when running brighter levels on a 10440 cell.

The LD01 is able to function on a 3.7V 10440 li-ion cell while still maintaining it's different output levels. Output on High is incredibly bright when running on a 10440 cell. This also means that you have to be careful of over-heating due to the small size of the LD01, heat will build up pretty fast. Runtime performance on an AAA cell is good in terms of both runtime and regulation.

Fenix advertises the LD01 as being able to provide a visually consistent output without any PWM effects. During my tests however, there was visually noticeably PWM effect on both Medium and Low brightness levels. Fenix advertises the LD01 to last up to 8.5 hours on Low, though I doubt it can achieve this even on a lithium AAA cell.

The Good - Maintains good output, runtime and regulation on a regular AAA cell. well-focused beam profile from a light this size. Fit and build quality is great.

The Bad - Finish has some minor but noticeable marks and scratches. Noticeable PWM effect on Low and Medium level in spite of the manufacturer advertising otherwise.

The Relative - Neutral white beam color. Some minor beam artifacts and slightly lopsided corona. Uses a twist activated switching mechanism. Able to tail stand.

Head (front view)

Head (side view).

Head (rear view).

Battery tube (front view).

Battery tube (side view).

Battery tube (rear view).