Rival Arms RA43G001A Slide Back Cover Plate Double Stack Black Anodized Aluminum for Glock 17/19 Gen3-4
https://www.tandktactical.com/shop/788130029510-rival-arms-ra43g001a-slide-back-cover-plate-double-stack-black-anodized-aluminum-for-glock-17-19-gen3-4-23094
https://www.tandktactical.com/web/image/product.template/23094/image_1920?unique=e926809
This Slide Back Cover Plate is CBC machined from aluminum with a black anodized finish.