Body and contacts are made of tool steel; hardened, ground, and lapped to close tolerances for diameter and concentricity 98-329-6 Cylindrical contact mechanical edge finder: 1/2" head diameter, 1/2" shank diameter, 0.0002" accuracy 98-326-2 Conical/cylindrical contact double-end mechanical edge & center finder: 0.2" head diameter, 1/2" shank diameter, 0.0002" accuracy 98-322-1 Cylindrical contact mechanical edge finder: 0.2" head diameter, 1/2" shank diameter, 0.0002" accuracy 98-325-4 Conical/cylindrical contact double-head mechanical edge finder: 0.2" head diameter, 3/8" shank diameter, 0.0002" accuracy 4 piece set includes 2 double-ended edge & center finders and 2 single-ended edge finders. Locate work surfaces quickly, easily, and accurately with edge and center finders. This set of 4 works with flat straight edges, shoulders, grooves, round work, studs, dowels, or center points and scribed lines. Body and contacts are made of tool steel; hardened, ground, and lapped to close tolerances for diameter and concentricity.