Mandrel Set fits 1" x 8tpi Headstock Thread on 1" x 8tpi screw on. Includes long mandrel, knurled nut, seven 7mm bushings, 7mm drill bit. Compatible with all PSI bushings and kits. Our precision mandrel sets inlude lathe accesories necessary for making "Slimline" pen and pencil sets. Mandrel has an OD of .243".