Now you can add sling swivels to your Mossberg 590 or 835 without altering your shotgun. Uncle Mike's Magazine Cap Swivel Sets have a factory magazine cap with the swivel base already installed. Just unscrew the factory magazine cap and replace it with the new cap. For the buttstock, a 3/4" wood screw swivel base is included, along with two Super Swivels. Product Specifications Includes: Replacement magazine cap with swivel base, 0.75" wood screw buttstock swivel base, and two 1" Super Swivels Fits Mossberg 590 and 835 12 gauge pump action shotgun