The No. 4 Concave Cutter is standard size at a length of 8″ long. The cutting edge on the No.4 is rounded making these act as a concave cutter and a knob cutter in one tool. These work well on all sizes of bonsai. Concave cutters are designed to create a clean concave cut. You can use them to cut branches and other things or use them to make the edges of wounds cleaner.