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:

Great video, Mike.  For those reading/watching...this model reviewed should not be confused with the older M300V version with 150 lumen white light output.  Be aware when purchasing which head you're buying.

Sure would be nice if those of us with the older M300v could send ours in for an upgrade for a cost.

The 600v also got a bump to 350 lumens white light.  I purchased both old models 60 days before the new versions came out.  Bad timing  as the white lights on the older versions are bad at best

I thought they discontinued the tan models.  Isn't this a new product?

The old ones came in tan and came with a pressure switch.. The new ones have more lumens but no pressure switch just clicky.

Also if you wanna upgrade you could just buy the head, I think that's the only difference I would think.