FCW Extreme Duty SS Mag Extension Spring 52 in Stainless Steel. This spring will also work with most 12ga and 20ga shotguns. This spring may need to be trimmed to length for your application. Specifications for FCW Extreme Duty SS Mag Extension Spring: Manufacturer: FCW Color: Stainless Steel Magazine Capacity: 5 Round Gun Type: Shotgun Package Contents: FCW Extreme Duty SS Mag Extension Spring FCW 15689: Extreme Duty SS Mag Extension Spring 52 in Stainless Steel