I had these Aluminum Mainspring Housings custom machined out of 6082-T6 Aluminum. This is the same aluminum used in the racing bikes on the tour de france. I then bead blast them to a perfect matte finish. The Aluminum Mainspring Housing weighs in at only 17 grams which is 2.6 times less than the same MSH made out of steel. They come ready for your favorite gunsmith to install or add his own texturing pattern. So do you really want that Plastic MSH in your $900+ gun?