The Spark ST6 is available in two variations, the ST6-460NW (460 lumens, neutral white) and ST6-500CW (500 lumens, cool white). The model reviewed here will be the ST6-460NW. The ST6 is among the most powerful headlamps available to date, however Spark has been careful not to over do it due to the relatively small body size and its ability to disipate heat. Up the front the ST6 has a smooth removeable bezel which allows the swapping out of the default clear glass lens with the included diffuser glass lens. While the bezel has not knurling, the slightly matte surface finish of the anodizing provides sufficient grip. Behind the lens is a lightly textured aluminum reflector with the LED sitting well centered at the bottom of the reflector cup. I noticed a couple of odd bumps on the reflector, but the polished finish is smooth and consistent, not affecting the beam profile. The exterior of the head has an ample array of cooling fins which helps nicely with dissipating the head from the high power LED. A digital push button switch sites slightly recessed on the side. It's easy to activate by feel when the ST6 is worn. The digital switch has really short travel and a muted clicking feel. This also means that momentary activation is not possible.

The ST6's body has a T-shaped design with the battery tube positioned perpendicular to the head section. With a battery loaded, the ST6 can feel a little front heavy when worn, I would recommend using it over cap which helps quite a bit. The battery tube has a clean and smooth design with knurled sections on either end, one of it being the battery cap. Knurling is very aggressive, the entire ST6 body gives an overall feel very similar to that of Zebralights in terms of fit and finish. The ST6 can be stood on either end of the battery tube allowing the light to be pointed horizontally on flat surfaces.

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

The Spark ST6 is capable of 5 output modes in total, inclusive of a temporary "Super" mode. Cycling of output levels is done by holding down either of the switches for about a second. The last output level is memorized even after the light is switched off. Note that holding down the switch to change output level will start cycleing from the currently selected output level (this is different from the SL6). The sequence of output levels are as follows:

Off > Min > Med1 > Med2 > Max

The "Super" output level is activated by a double tap on either of the switches. I noticed that the double tap has to be at a certain interval, pressing it to quickly ends up switching the light off. Also note that the "Super" level will only run continuously for 5 minutes to protect the light from the excessive amount of heat radiate and will step down to the Max output level. Beam profile is nice and clean with an intense narrow hotspot with a minimal corona region. The spill beam is very wide which is more practical in a headlamp, providing much better peripharel illumincation. As denoted by the model name, the beam has a neutral white tint. As can be seen from the graph below, the runtime and regulation performance is impressive. When comparing to the SL6, we can see the regulation isn't as tight on the "Max" level, this is probably due to the light coping with the heat in its smaller body.

The Good - Solid regulation and runtime performance. Clean fit and finish.

The Bad - Nothing significant.

The Relative - Clean beam profile with a neutral white tint. Digital push button doesn't allow for momentary activation. Is able to side stand.