CMT 529.254.31 Plug Cutter, 1-Inch Minor Diameter, 1-15/32-Inch Diameter, 1/2-Inch Shank 4 Cutting Edges, 5-1/2-Inch Overall Length. Max suggested RPM: 300 on hardwood, 500 on softwood. Made of alloyed steel, long-lasting cutting performance. For making plugs in soft and hardwood.