American Precision Arms Fat Bastard Gen 1 Muzzle Brake 3/4x24. they set out to design a muzzle brake that would actually tame the 338 Lapua. This brake is meant for Larger barrels that are generally required by the 338 Lapua. All of the require installation by a competent gunsmith. By properly fitting this brake you can achieve a perfect seamless fit on your rifle as well as perfect coaxial bore alignment. Please see the video for further information. Specifications for American Precision Arms Fat Bastard Muzzle Brake: Manufacturer: American Precision Arms Color: Stainless Projectile Caliber: .338 Caliber Caliber: .338 Lapua Magnum Finish: Plain Fabric/Material: Stainless Steel Threads per Inch: 3/4x24 Model Generation: 1 Inner Diameter: 1.115 in Outer Diameter: 1.115 in Length: 3.3 in Weight: 6.8 oz Package Contents: American Precision Arms Fat Bastard Muzzle Brake American Precision Arms G1F34GSS: Fat Bastard Gen 1 Muzzle Brake 3/4x24