This ultra-rigid lightweight aluminum unit straddles both sides of the receiver and is crafted with a non-glare anodized finish.The top picatinny rail can mount a variety of accessories, yet is designed to sit just high enough to allow continued use of the shotgun's bead sight.This rail mount incorporates a slimline sidesaddle shotshell carrier made of flexible synthetic rubber to keep six (6) extra shells in readiness.This model fits 12 gauge mossberg 500 and 590 models.Shell Count: 6Type: Shotshell CarrierColor: BlackMaterial: Polymer w/Aluminum Mounting PlateSize: 6 RoundsModel: Sidesaddle Rail MountFinish: MatteModel Fit: 500, 590Mount Type: ReceiverCaliber Or Gauge: 12 Gauge