The Shure PS21US Power Supply is a direct replacement for the Shure PS20 power supply. The PS21US is an in-line power supply (120V ac) for models 200M, FP22, FP24, FP33 mixers, the P4M and P4T PSM Receivers, and the SLX4, T3, T4V, T4G, T4N, T88 and LX88 Wireless Receivers.