Gorilla Machining .45ACP Glock compatible BCG was specially built for .45acp AR-15 Carbines. This BCG works with Glock lower receivers. The carrier body of these Bolt Carrier Groups is made from 8620 Steel with a tool steel extractor bolt carrier group. This Bolt Carrier group is nitride QPQ Treated with a Rockwell rating of 72 giving you the hardness needed to last. It is fully assembled ready to install.