Starrett 569AXP Tube Micrometer, Plain Thimble, Carbide Faces, 0-1" Range, 0.001" Graduation, 3/16" Min. Hole Size Vertical cylindrical anvil for measuring tubing wall thickness Vernier scale in inch units for taking precise outside diameter (OD) measurements Black enamel finish for protection and durability of frame High-grade tool steel construction for durability Micro-lapped carbide spindle face helps provide accuracy and wear resistance