This is the REVO® SFM-B1 (Straight, Type B Skid) #A-5764-0025. SFM-B1 small straight module for short lands (type B skid). The B-series of modules features a small skid which allows the stylus to be placed close to the edge of surfaces of interest. The range of skid-arm designs provides access into awkward to reach features and parts with surface form and curvature.