Series 146 Satin chrome finished frame. Designed for measuring grooves, recesses and shoulders located inside a bore. They measure not only thickness and spacing of grooves, but also measure from an edge to a land, or from shoulder to groove. Spindle hardened and precision ground, with micro-lap finish on measuring face. Every thousandth is numbered for easy reading. To measure: width of groove, width of land. To determine: location of groove, depth of bottom of groove. Accuracy: parallelism: 10µm. Instrument error: ±10µm. Inch - Graduation: 0.001".