These wrenches are used to remove the castle nut that hold on the gas block on Knights Armament Mod 2 gas blocks. They will work on both SR-15 and SR-25 versions.
They come in a narrow and wide tooth version. Please measure the tooth size and order accordingly. Historically earlier production rifles use the narrow tooth size.
Narrow tooth width - 0.125"
Wide tooth width - 0.178"
Mod 2 castle nut torque value - 25 ft lbs