Forward Controls Design 4140 End Plate w/Rear Facing QD Sling Swivel Socket Black ESF-H1 BLK DLC. ESF-H1 is machined in 4140 steel and coated in DLC. It does not have rotation limiters as the QD sling swivel is prevented from rotating 360 degrees by the receiver extension. Specifications for Forward Controls Design 4140 End Plate w/Rear Facing QD Sling Swivel Socket: Manufacturer: Forward Controls Design Color: Black Finish: DLC Fabric/Material: 4140 Steel Gun Make: AR Platform Package Contents: Forward Controls Design 4140 End Plate w/Rear Facing QD Sling Swivel Socket Forward Controls Design ESF-H1 BLK DLC: 4140 End Plate w/Rear Facing QD Sling Swivel Socket Black