Abstract: A lithotripter reflector is disclosed which has an ultrasound transducer mounted at the open end of the reflector and on the axis of rotation. The transducer is supported in a brass socket, and a pair of oppositely directed arms are aligned with one another and extend in opposite directions from the housing. The outer ends of the arms are provided with steel blocks which are ground to precision size. The blocks are received in carefully milled sockets in said reflector so that insertion of the blocks in the sockets accurately positions the housing and hence the transducer.