Side mounted shell holder with picatinny rail mount, built for Mossberg 500 and 590 Series shotguns. Accommodates up to seven 20 gauge shotgun shells. Ambidextrous design for installation on either side of the stock. Two piece design mounts together as a single unit into factory mounting holes with no additional gunsmithing required. Also compatible with Mossberg Shockwave, 535, 835, and 590a1 models.