This is a Bravo Company known as the MLOK Rail QD Sling Mount, model BCM-MCMR-SM.
Bravo Company's BCMGUNFIGHTER MCMR-SM Quick Detachable Sling Mount" M-Lok Compatible is low-profile for increased mobility and decreased snag factor. It fits a standard push button" quick detach sling swivel (not included). It has an 8 position (360 degree)" non-rotational locking interface and all steel construction.
Features:
Compatible with M-LOK® mounting system
8-position (360°) non-rotational locking interface
