Guide to Geometry/Feed: -GM geometry is the basic choice for most materials. Medium feed. -LM geometry is the best choice for long chipping materials, e.g. low carbon steel and stainless steels. Medium feed, insert with sharp positive edge. -GR geometry is the high feed choice for steel and cast iron. Insert with strong reinforced edge, suitable for roughing. -GT geometry is a problem solver for unstable conditions and interrupted cuts. Low to high feed. Good chip control in most materials.