Tacstar's slimline sidesaddle helps to improve reload capabilities and efficiencies for shotgun receivers.It utilizes a non-glare, anodized aluminum backing plate with a contour to the plate so that it takes up less space on the receiver, while the shell carrier itself is made of flexible synthetic rubber material.This model is compatible with your 12 gauge mossberg 930.Shell Count: 6Type: Shell HolderColor: BlackMaterial: Polymer w/Aluminum Mounting PlateModel: SlimlineModel Fit: Mossberg 930Mount Type: ButtstockCaliber Or Gauge: 12 GaugeCompartments: 6