The main types of surface roughness gage probes available include general purpose probes, small bore probes, groove probes or groove bottom probes, traverse chisel probes, and parallel chisel probes. Each of these types of probes is best suited for a particular kind of measurement. Many metrologists can get by with only ever using the general purpose probe for common surface roughness measurements. However, when working with more particular surface contexts, you will likely require the probe that is intended to be used in that context. When measuring surface roughness of small holes, you will want the small bore probe. When measuring surface roughness of the bottom of an “O” ring groove, a recess, or a hole with a depth up to 6.0mm, you might use the groove bottom probe. Traverse chisel and parallel chisel surface roughness gage probes are best used to assess roughness in a gaging sharp edges or small outer diameters, and differ the surface angle they are placed in.