Handy to have. The Samson SWA500UK PSU is incredibly useful for live sound engineers. When youre out on the road you need to be prepared for anything. This sometimes means having two or three of everything. The SWA500UK PSU serves as a replacement powerful supply for Stage 5 and 55 Airline 77 and Concert 77 wireless systems. With this handy supply youll be one step closer to taking on any unforeseen scenario that touring throws at you!