The Evolution Gun Works 9mm Post-Ban style compensator’s have a .900″ diameter. This compensator was created due to a federal ban that became the rules for several states. This compensator is not a flash hider, but a muzzle brake. So it’s perfect for those of you looking to build a Pistol Caliber Carbine in a state that has tough regulations. The overall length of this compensator is 1.75″ with a thread count of 1/2 X 36.