6061 T6 Hard Black Anodized Aluminum 1/2x28 TPI Barrel Extension Tube Muzzle Brake For 223 .22 and 5.7x28  and also for 9mm

Center Exit Hole Diameter:  Dia. 11 mm

it is one solid piece structure.

High quality aluminum Billet 6061 T6 alloy CNC machined to spec

1/2x28 TPI 

It structured a set screw, only with a L wrench Tool can be tightened and/or removed

Total length: 7"

Diameter: 1.24"

Thread on worked as a 6.5" barrel extension fixed by a set screw and can only be removed by a L wrench Tool.