 The blade geometry is defined by a semi-standardized numbering system that varies by manufacturer and country of origin.For each gouge a "sweep number" is specified that expresses the part of a circle defined by the curve of the blade.The sweep number usually ranges from #1, or flat, up to #9, a semi-circle, with additional specialized gouges at higher numbers, such as the U-shaped #11, and a v-tool or parting tool, which may be an even higher number such as #41.