Thorntail2 Picatinny SBR Light Mount: Saves Weight / Eliminate Components / Improve Adjustability: By removing the factory thumb-screw 1913 rail mount from Surefire's M300, M600 Scout and Streamlight Protac Railmount 1, 2 & HL-X, directly attach your Light to Thorntail 2 SBR via the two threaded holes in the square lugs on your Light with our included hardware. This saves weight, provides adjustability and reduces light height on your firearm.