53-670-038-0 Fowler Rectangle Gage Block Set, 36pc Grade 0Fowler Steel Rectangular Gage Block Set 36 piece set Grade 0 Each block is rectangular steel and hardened to 65RC, stress relieved, lapped to accurate size, parallelism and flatness, then carefully inspected and marked for size; designed to meet close tolerances Each set includes standard sizes found in more expensive sets. Each block individually serialized; conforms to rigid standards of the National Institute of Standards & Technology Price