Mitutoyo 323-350 Digimatic Disk Micrometer, Inch/Metric, 0.787" Dia. Disks, Ratchet Stop, Rotating Spindle, 0-1" (0-25.4mm) Range, 0.00005" (0.001mm) Resolution, +/-0.0002" Accuracy, Meets IP65 Specifications Micrometer measures 0 to 1.0" (0 to 25.4mm) with 0.00005" (0.001mm) resolution and + or - 0.0002" accuracy, for measuring the root tangent length of spur gears and helical gears LCD screen displays in inches and metric units Measuring disks are flat with a center recess, are 0.787" (20mm) in diameter, and have an edge thickness of 0.028" (0.7mm) for use in narrow spaces Ratchet stop to help provide uniform pressure for precise, repeatable measurements Ingress Protection certified IP65 for protection against dust and water