Well the shaft is a 1 1/4" and the shaft log measured just after the rubber hose is 2 11/16, if I measure the stuffing box diameter it reads as 2 1/2" so I figure it should be a 2 5/8" but it would be nice to have someone confirm the size needed. I am going to order soon, email if you can the answer Thanks solutions@corellianconsulting.com Andy Bogaart