ESF (End plate, Sling Adapter, Forward Controls Design) is a drop in end plate replacement for the AR platform (both 223 and 308 spec). Featuring three quick detach sling swivel sockets (two side, and one rear facing), when used in conjunction with a castle nut, ESF will allow retractable carbine stocks to fully collapse. SOPMOD and B5 Systems Bravo stocks will fully collapse with a rear facing QD swivel installed, other carbine stocks must be closed on the #2 position on the RE (#1 position being fully closed) if a rear facing QD swivel is present.
ESF is available in 7075 anodized, or 4140, black nitrided versions. Both ESFs haverotation limited, or non rotation limited side facing sockets option. The rear facing socket has no limiters, as the receiver extension effectively limits the swivel's rotation.
As is our practice, ESF's shape is dictated by its functions. In order to accommodate the rear facing socket, and fill one of the design requirements that ESF must be able to use stakable castle nuts and allow the carbine stock to fully collapse, ESF has a slight increase in width on the sides, and small openings on the top of the sockets housing. These design cues do not affect ESF's structural integrity, and mostly go unnoticed by users, they merely reflect a paradox, that it can be quite complicated to create a simplified design. A seemingly simple product can often be more than meets the eye.
Aesthetics were never a part of the stated objectives for ESF. Nevertheless, ESF, like similar products before it, effectively lengthens the carbine receiver's rear and gives it an AR10/SR25 like silhouette. We've long considered the AR carbine's rear seems to be abruptly terminated which leaves a gap between the end plate and its retractable stock. ESF fills the void and, the classic AR15/M16 lines flow far better with it. Even though we take a dim view of fashion firearms and components, we can still appreciate aesthetics, especially if they stem from the design's functions :)