Interchangeable V-Anvil type for measuring pitch diameter Each anvil can be used for both metric and unified external threads. The correct pair of anvils must be selected and inserted in the hollow micrometer spindle and anvil. The micrometer anvil is fully adjustable by the knurled knob located on the anvil side of the frame. Zero set the micrometer with this knob whenever the anvil is interchanged. 60° V-Anvil and Conical Spindle are made of high-grade special steel, hardened and precision ground. Ratchet stop facilitates uniform and consistent measurements. Furnished complete with fitted carrying case and appropriate standards.