D...
Review confirmed by purchase 
This is a cast aluminum part, something that is not mentioned in the product description on Militaria (it just says metal, which doesn't say much—just that it's not plastic). I am writing about this because it affects the rail's durability and strength. In my case, it will be used with a Feinwerkbau pistol after some minor modifications. It seems quite solid and rigid, and the casting and coatings are well made. Maybe steel would be better, but since it's intended for airsoft, it probably doesn't need to be that tough.
