Machined from 416 heat treated stainless steel, no part on the carrier is MIM (metal injection molding). The black carrier has a Micro Slick coating, whereas the grey is not MS coated to show its stainless steel finish. Instead of the traditional alignment key they have two heat treated screws that are also roll pinned onto the carrier. To ensure easy service of your carrier, they used a proprietary firing pin retainer that can be removed with ease, instead of a cotter pin. Being able to easily service your carrier will add to it's life.