Check the listing for details. Mini Shell Adapter / Follower Kit for Mossberg Pump Shotguns **NOT OpSol**. Color: Black, Condition: New. Listed at 29.00 USD. ** THIS KIT UPGRADES LEGACY 12-GAUGE MOSSBERG 500, 590 OR MAVERICK 88 FIREARMS TO 590S FUNCTIONALITY ** This kit contains our Patent Pending Universal Cartridge Adapter and Low-Drag No-Snag Magazine Follower which allows cycling of 1-3/4" Minishells up to 3" Magnums in the same magazine. The adapter is constructed from vulcanized thermoplastic rubber, and the follower is machined from solid 6061-T6 billet aluminum. This kit is compatible with all Mossberg 12-Gauge pump-action firearms with machined grooves in the receiver (refer to the picture or the installation video to confirm your firearm's compatibility). Please note there may be a short break-in period for some adapters after installation. Cycle a few magazines of full-size shells if you initially experience issues with 1-3/4" shells, please reach out to us if problem persists.