No they are made of Hi Impact PVC, very strong stuff. I chose this because I have 2 Gamo Shadow Hunters and one of the brakes got scratched and touching it up with a black marker, it still shows the scratch, and I checked to re anodize it cost more that buying a new one form Gamo.
These you just remove and repaint, and they don't weight a bunch.
I have aluminum if you want one made of that, I have aluminum stock up to 3 inches in diameter.