Surefire Scout lights are known for their small size and durability and the M300V is no different. I've had mine for a couple years and used it primarily when using NV optics but it certainly works well in white light settings as well.

Another benefit of the Scout lights is the ability to interface with tons of aftermarket mounts which is huge. It lets you mount it just about anywhere you wish with a variety of hand guard options out there. The light also comes with a clicky tail cap as well as a pressure switch end cap so you can configure it as you wish there as well.

Basic specs:

Bezel Diameter: 1.125 inches
Weight: 4.5 ounces
Batteries: 1 123A (included)
Output High White: 250.0 lumens
Runtime High White: 1.2 hours
Output High Infrared (mw):100.0 mW
Runtime High Infrared: 5.0 hours
Tactical Runtime, White: 1.2 hours

Below I do some shooting with it mounted on a few rifles and go over all the details of the light, compare the beam to a few other popular weapon lights, and discuss what I think of it overall: