Select which size you need - these are available to mount to either 1-1/4″ x 8tpi shafts or 1″ x 8tpi shafts. These adapters allow you to mount your CBN sharpening wheels onto your lathe shaft for slow speed grinding (you can turn your lathe WAY down) using either your tool rest as a support post, or you can mount your sharpening jigs to the lathe. The 5/8″ shaft accepts most CBN wheels. The end of the mandrel is designed to accept your tailstock live center for support – USE THIS. IMPORTANT – KEEP YOUR LATHE SPEED BELOW 2000 RPM.