Q Rearend Muzzle Brake M18x1. Same taper system. Same solid performance. Just added wrench flats so getting it on (and off) is easier and a lot less dramatic. Specifications for Q Rearend Muzzle Brake: Manufacturer: Q Color: Black Features of Q Rearend Muzzle Brake Keeps the tapered mount system you already trust Adds wrench flats for easier install Plays nice with barrels that have 90-degree shoulders Gives you the same clean solid lockupjust simpler to work with Package Contents: Q Rearend Muzzle Brake Q RE-CBXL-M18X1: Rearend Muzzle Brake M18x1