Title says it all. I've got a barrel for a Glock 21 chambered in .400 Cor-Bon. It is extended and threaded. Not sure what the thread size is. Comes with a compensator that looks an extended slide. It's in pretty good condition and appears to have never been fired. The coating on the compensator shows wear from rattling around in a parts box for a few years. $150 or trade for an SKS.