This works perfectly for mounting a right-angle 18650 light like a Zebralight. This allows me to carry a spare battery, something almost unheard of in purpose-designed bike lights. No more sealed battery USB lights for me.
The rubber loops are very beefy but the light is easy to get on and off for commuting.
With a right-angle light there is no boucing or wobble of the beam and the light never unexpectedly starts pointing down after hitting bumps. It also allows the light to be directly over the stem instead of off to the side.