How light? Just under an ounce for the light and strap, and 1.6oz including the case, which is the big orange thingy at the top of the picture left. It has a clip to attach to a pack strap or hat brim. It even pans and tilts. Waterproof to 3 feet (or, as they say in the godless socialist regimes, 1 meter), it has five modes: dim white, bright white, strobe white, bright red and strobe red.
Powered by two lithium watch batteries it has a supposed burn time of 35 hours on bright white (illumination to 19 meters) or 45 hours on dim white (11 meters). This is not a primary light for working major projects or filming porn, but it’s the best just-in-case shiner out there right now. Buy it, throw it in your pack and forget about it until you really need it.