Mossberg 590S, Optic Ready, Pump Action, 12 Gauge, 3 Chamber, 20 Barrel, Matte Blued Finish, Synthetic Stock, Bead Sight, Receiver Milled for Shield RMSc Pattern Micro Dot Sights, 13 Rounds, Cycles 1.75, 2.75, or 3 51604 Mossberg 590S models set a new standard for shotshell cycling flexibilty. Now, we've added the added benefit of optic-ready convenience. Receiver cuts allow 590S shotguns to accept low-profile direct mounting of Shield RMSc-pattern micro dot sights, for improved eye alignment and target acquisition. Cover plate is included when a sight is not mounted.