Mesa Tactical SureShell, 6-Shell Side Saddle with 4 3/4 Rail, Fits Moss 500/590/Mav 88, 12 Gauge, Matte Finish, Black 94880 This SureShell Polymer Carrier system features shell holders injection molded from glass filled polymer" secured to the receiver by a lightweight aluminum back plate with brass threaded inserts. The SureShell Polymer Carrier also includes an innovative dual rubber friction system that reliably holds shotshells in place. The saddle rail feature Picatinny rails machined from aircraft grade 6061-T6 aluminum" which are mil-spec hard anodized and provide an extremely durable non-glare matte finish. The saddle rail design provides a robust mounting platform suitable for mounting a variety of optical sights and also includes a six shell SureShell polymer shotshell carrier mounted on the left side of the receiver. Manufactured in compliance with MIL-STD-1913 Picatinny specifications" and no gunsmithing is required for installation.