Bastion slide back plates are made of T6 machined aluminum, hard coat anodized black and Lasered. Compatible with Glock 17 19 21 22 23 24 26 27 29 30 31 32 33 34 35 36 37 38 39 40 41 Models Gen 1-4 ONLY. NOT COMPATIBLE WITH G42 OR G43 - NOT COMPATIBLE WITH GEN 5. Great replacement for a plastic factory part. You will love the quality of BASTION products. Many different designs to choose from our stock inventory. WE ALSO OFFER CUSTOM ENGRAVING