Barrel and Choke Tubes | Agency Arms Gen4 Compensator, Features Two Chamber Design-2 Vertical Ports And 2 Side Venting Ports, Front Sight Hole, Two Set Screws With An Allen Wrench And A Vial Of Rockset Are Included In Package, Compatible With The Glock 17/19/34, Standard 1/2 X 28 Thread Pitch, Black..