Diameter: measured perpendicular to the shank, this is the width of a full depth cut at the surface of the material.Ball – Ball bits are used to give a radius to the inside corners of pocket cuts. When used for 3D projects with low percentage stepovers, the radii help blend each path together, resulting in less finish work. A ball nose bit is a poor choice for profile cuts as the bit will have to go past the bottom of the material the radius of the bit into the spoilboard to get a clean profile.Ball-nose bitBall-end bitCore Box bitSingle flute “O” BitOther Geometry"O" flute: This is a relatively new wrinkle in bit geometry. The gullets of the O flute bit are designed to "roll" the shavings into a ball. The purpose of this property is to compact the shavings and make them easier to throw clear of the bit. This property is especially important when cutting materials that create lightweight shavings... like plastics.