The Surefire X300T-A is the upgraded (Turbo) version of the X300. Now punching with 66k Candela — the X300T is developed for maximum reach and able to pierce photonic barriers. The -B designation is to indicate this model uses a thumb screw mount — ideal for picatinny rails and metal framed pistols.
The light comes standard with a rocker switch as well as a pressure sensitive switch so you only have to push forward on the switch mechanism for temporary activation.
With 650 lumens, this light is plenty bright. The tight focus of the Turbo eliminates spill and barrel shadow on long guns and is an immensely powerful light for users that can illuminate and even temporarily blind attackers.