Shure UA 221, UHF Antenna Switch Set, For 2 SLX4 / BLXR diversity receivers, Passive, HF cable set and BNC mounting socket included, Suitable for the following receivers: BLX4R, QLXD4, UC4, SLX4, ULXS4, ULXP4, ULXD4, ULXD4D, ULXD4Q, U4S, U4D, UR4S and UR4D