Quoted:
What mount is that? ^
CUSTOM DEFENSIVE PRODUCTS - AR-15/M16 BAYONET LUG ACCESSORY MOUNT
50 bucks from brownells, obviously make sure you have a bay lug.
I took my surefire off a couple weeks ago and have been playing around with a TLR-4 that I got on sale for my pistol as a bunch of people here have suggested (light laser combo, but same paddle activation and toggle) and I didnt like it at all. I found that trying to manipulate the light was way to difficult to do while still mainting a good grip on the carbine. The surefire style is nice because you are pressing on a large simple button that is along the axis of the weapon, you can afford to be sloppy with fine motor skill or a poor grip and still manipulate the light. The streamlight is way to difficult to apply a pound or so of pressure circumferential to the bore on a very light toggle and not accidentally lock the light on all the way.
If you find a surefire setup to bulky, I agree the size and weight of the TLR is a nice advantage, but if that's what your looking for I would listen to Travis and with one of his style setups.
also the explosion of light you get from any of the number of the big boy sized tubes with upgraded internals is such a pleasant surpirse after using the smaller streamlights for a while.