This CMT multi-radius round over shaper cutter head can be used with 3 different knife pairs, each with 2 cutting radii. The result is you get 6 different round over radii with this head and optional cutters. The standard knives are 5mm (3/16-inch) and 10mm (25/64-inch) radius. Optional knives are 4mm (5/32-inch) and 8mm (5/16-inch) radius or 3mm (1/8-inch) and 6mm (15/64-inch) radius. They are for use on spindle moulder machines, double-end tenner and shapers. Ideal for solid wood and panel materials.