Mechanical tubular-rod inside micrometers use interchangeable hollow and lightweight rods to measure the inside dimensions of holes, tubes, pipes, cylinders, rings, and other parts. - The measurement is taken on the Vernier scale. Range / 1.5 in to 12 in Resolution / 0.001 in SPC Output / No Movement of Screw / 1/2 in Inside Micrometer Type / Tubular Inside Micrometer Number of Measuring Rods / 8 Number of Micrometers / 1 Operation Type / Mechanical Thimble Type / Plain Case Included / Yes Case Type / Wood Case Contact Point Material / Steel Contact Point Shape / Curved Features / Wide Range of ID Measurements by Combining Extension Pipes and Anvils with the Micrometer Head, Supplied in Fitted Wooden Case except 500mm/20 in Come in Plastic Case. Includes / Extension Pipes Maximum Measurement - Inch / 12 in Minimum Measurement - Inch / 1.5 in Rod Diameter / 8mm Rod Lengths Included / 0.5 in, 1 in, 2 in, 2.5 in, 3 in, 3.5 in, 4 in, 6 in Accuracy / +/-0.000425 in Maximum Measuring Depth / 12 in