CMT 529.158.31 Plug Cutter, 5/8-Inch Minor Diameter, 1-7/64-Inch Diameter, 1/2-Inch Shank 4 Cutting Edges, 5-1/2-Inch Overall Length. Max suggested RPM: 500 on hardwood, 1000 on softwood. Made of alloyed steel, long-lasting cutting performance. For making plugs in soft and hardwood.