ATI Outdoors Magazine Clamp, Fits 12 Gauge Shotguns, with Sling Swivel, Black SMC1100 The Advanced Technology Int. Shotgun Mag Clamp or 1" Light Mount and Sling Swivel Stud fits all 12 gauge shotguns. It strengthens the connection of the Mag extension to the barrel and may also be used to mount a 1" diameter light or laser to the barrel. Included is a sling swivel stud that is reversible for right or left handed shooters.