While both the UBR and Str come with type 1 push-button QD swivel sockets pre-installed on the left side of the stock, this sling mount kit - Type 2 can be installed on the opposite side to add additional push-button QD Sling swivels or our Own Magpul QDMA additionally, for running ambidextrous sling swivels on the SGA, MOE rifle, MOE Fixed, Hunter 700, and Hunter X-22 stocks, This type 2 kit must be utilized in conjunction with the optional type 1 kit. Heavy-duty black phosphatized steel construction easily installs with The UBR or STR's original hardware, or with the hardware included with the type 1 kit. Swivels not included. Note: the sling mount kit, Type 2 can not be used to run dual-side swivels on the ACS or ACS-L stocks..