Koyo Quality Spherical Knob Cutter 8"
Knob Cutters are designed for removing unsightly knobs from trunks and branches without leaving protruding callous when the cut heals. _They can also be used to further hollow out the cut after a concave branch cutter is used.
Be careful not to overdue it with your knob cutter, they can take out more material than you expected
Though not usually a beginner's tool, most serious bonsai enthusiasts wouldn't be without one.
Made in Japan by Koyo, a quality tool maker