Bell & Gossett 1/2″ x 1/2″ coupler for PD-35 and PD-37 booster pumps, as well as, 60 series AA pumps. A broken coupler indicates that the motor mounts have lost their resiliency and the motor shaft and pump shaft are now out of alignment. It is recommended to replace the motor mounts when the pump coupling breaks. Spring Coupler for #5 Bearing Assembly (1/2″ x 1/2″)