Fowler 52-229-210 Outside Metric Micrometer, 25-50mm Measuring Range, +/- 0.004mm Accuracy, 0.01mm Graduation Outside micrometer with choice of measuring range and flat anvil/spindle pair for general purpose measuring Vernier scale has 0.01mm graduation intervals and an accuracy of 0.004mm for precise readings Carbide-tipped measuring faces provide wear resistance and long life Friction thimble with ratchet stop applies constant force for repeatability between users Insulated frame helps reduce temperature-related expansion or contraction