The SI Multi-Function End Plate and Anti-Rotation Castle Nut has an anti-rotate QD socket or sling loops built in. It also is reversible, has three integral sling mounting options, a traditional sling loop, and a loop for hook style attachments.
Specifications:

Type	Castle Nut/End Plate
Model	AR Style
Dimensions
Size
Material	Steel
Action
Trigger
Safety
Thread Pattern
Finish	Black
Bolt Type
Hand
Hammer Type
Max Capacity