The Femto is a great choice for an inexpensive rear light. Is has two distinct features which make it a top choice in it's category. First, it has an astonishingly simple mounting system that will attach the light to just about any surface or rounded profile. The semi-tacky silicone strap clips on a hook that is located on the back of the light and pulls around the object you are mounting it to, then secures to a hook on the other side of the light. The silicone composition on the strap and inside of the light offers lots of grip and dampening, so the light will not migrate or rattle while you're riding. The second standout feature is how you operate the light. The lens acts as both a lens and a button that you push to turn the light on and push again, to turn the light off. Simple and brilliant design that foregoes the pesky button or switch design that is normally found on the exterior of the light body.
The Femto's body is constructed of CNC's alloy for durability and longevity. This body unscrews to replace the standard CR2032 battery that powers the unit. Burn time is a 30 hours on sustained setting and 60 hours on flashing mode. The LED puts out a solid 7 lumens and total weight is a scant 21 grams. The Femto has to be one of the best value in inexpensive rear lights on the market.