This is a TacStar Side Saddle, model 1081168.
TacStar's new 4 round SideSaddle Shotshell Carrier is the perfect accessory for all your hunting shotguns. The 4 round SideSaddle mounts easily to the side of the receiver and requires no modifications to the shotgun. Designed to provide clearance for long forends.
Features:
Corrosion Resistant Polymer Shell holder
Rugged, Aluminum Backing Plate
Easy Mounting