The APOLLO S from Ultradyne provides competition level recoil reduction and muzzle control. This compensator has 1/2x28 barrel threads, with a simple 5-port design. By using a scientific approach and studying thousands of recoil events. Ultradyne engineers have struck a balance between extreme recoil reduction, virtual elimination of muzzle rise, and less aggressive venting of gas. The Apollo S is perfect for shooters who want drastic recoil reduction with less perceived blast. The perfectly sized 5-Port design evens out the recoil event which produces an ultra smooth shot like no other compensator. A timing nut is included for easy installation. Perfect Balance Extrem Mfg: Ultradyne Usa