Starrett 73A-12 Solid Nut Inside Spring Caliper, Steel, Flat Leg, 0-12" Range Bow spring is flexible yet strong to assure reliable measurements Legs made of flat stock for durability High-grade steel is rugged Centrally located adjustment to ensure smooth action Curved tips for transferring the measurement of the internal size of an object Made from high-grade steel Legs made of flat stock Fulcrum stud is hardened Exceedingly strong bow spring