Big Horn 17042 4-Inch Outside Caliper Big Horn outside calipers is a useful measurement transfer tool when working with round stock or oddly shaped materials and then transferring that measurement to a ruler The forged steel legs on this caliper feature hardened points for precise marking of the work piece An adjusting screw has a self-seating washer and nut to permit quick and positive adjustment Hardened and tempered bow springs and fulcrum spools assure uniform tension without side play while using this outside caliper Steel construction with hardened fulcrum for durability Threaded spool mechanism for flexibility