These SureShell shotshell carriers for Mossberg 500 and 590 shotguns feature integrated top picatinny sight rails for enhanced versatility. Designed to mount using the factory top screw holes found on Mossberg 500 and 590 models made since 1997, these carriers securely attach to the left side of the receiver for a stable and streamlined fit. Precision-machined from aircraft-grade 6061-T6 aluminum and mil-spec hard anodized, the picatinny rails offer exceptional durability with a non-glare matte finish, ensuring both rugged performance and a sleek, professional look.