This air pump is for units with caralytic air pumps and fits the Prochem Performer, Performer 405, Bruin, Bruin II, Legend and Legend SE units. When testing an air pump vacuum it should register beterrn 20-25 Hg. Service replacement intervals are 1,500-2,000 hours, based upon inspection. Part is sold without sheave (pulley), we recommend purchasing the sheave in conjunction with the part because damage may occur during removal.