Q Rearend XL Muzzle Brake .338 Bore M18x1.5 Brass. Just with a little more grip. The Rearend is for barrels with 90-degree shoulderswhere you want everything lined up clean and tightened down without fighting it. Same taper system. Same solid performance. Just added wrench flats so getting it on (and off) is easier and a lot less dramatic. Nothing new to learn here. If you like the Cherry Bomb youll feel right at home. Specifications for Q Rearend XL Muzzle Brake: Manufacturer: Q Projectile Caliber: .338 Caliber Threads per Inch: M18x1.5 Features of Q Rearend XL Muzzle Brake: For Barrels with 90-Degree Shoulders Package Contents: Q Rearend XL Muzzle Brake Q RE-CBLX-M18X1.5: Rearend XL Muzzle Brake .338 Bore M18x1.5 Brass