Features: High-quality alloy measuring heads for various internal size measurements, fine workmanship with no burr. Clear laser marking lines for easy reading. Main micrometer body made of stainless steel with chrome-plated surface, wear-resistant and durable. Equipped with a locking device; precise mechanical structure allows for intuitive and convenient reading. Built-in ratchet stop ensures accurate and repeatable measurements. Specifications: Type: Inside Micrometer Measuring Range: 5mm30mm Material: Stainless Steel Precision: 0.01mm Weight: 268g (approx.) Zeroing Procedure: Clean the measuring anvil surfaces with a soft cloth, then rotate the micrometer until the two measuring surfaces are in contact. If the zero lines on the thimble and sleeve are not aligned, adjust using one of the following methods: Method I: If the error is less than 0.02mm (0.001"), use the ratchet stop to lock the spindle, then use the wrench to rotate the sleeve until the zero lines align. Method II: If the error is greater than 0.02mm (0.001"): Step 1: Lock the spindle with the ratchet stop, then use the wrench to loosen and remove the ratchet stop and thimble. Step 2: Realign the zero lines of the sleeve and thimble, then reinstall the ratchet stop. Fine-tune if necessary using Method I. Note: Calibration is not required during normal use. Only calibrate if the micrometer shows significant wear. Package Includes: 1 x Inside Micrometer 1 x Wrench 1 x Calibration Ring 1 x Packing Box Note: New and old versions of this product may be shipped at random. Please confirm you are comfortable with this before placing your order.