PEM Grand National Centerless Tube for Quick Change Rear End 24in Tube PEM Centerless GN Tube for Quick Change Rear End. 188" Wall Centerless Ground Steel Tubing 24" Long Retainer bolt holes must be drilled and tapped after installation This tube fits 60" Centered Quick Change Fits Quick Change Side Bell GN 2.5" Bearing Snout Part# PEM TWSnout24 QCB.