These brakes are made to fit within 3-Gun style competition rules and are designed to be the most effective within those requirements. Made from 4140 steel.The 3-Gun brake is also extremely effective on bolt guns and precision rifles, like the new Ruger Precision Rifle or RPR. In fact, It is so efficient, that on calibers under .308win there is virtually no performance difference between the 3-Gun and the larger HexMod brake, and even on a 300winmag it will reduce recoil to .243 levels (vs. 223 levels with the HexMod).Due to the rear diameter of this brake, it looks best on barrels measuring smaller than .830". 5/8-24 accommodates calibers up to .338