Master Grade: 5/8" blades, 8" overall length The solid stainless steel construction of these Knob Cutters gives them the feel of fine surgical instruments and provides a lifetime of easy care and superior use. The durability and ease of maintenance of these tools is second to none. SPHERICAL KNOB CUTTERS - Known in Japan as Kobu iri Hasami, these cutters are designed for removing trunk knobs and roots. The head is shaped like a ball,hence the name 'Spherical'. They produce a hollow, circular cut that heals quickly and with a minimum of scarring.