Feature: High quality alloy measuring heads can be used for various internal size measurements, fine workmanship and no burr. Clear laser marking line for convenient reading. The main body of the micrometer is made of stainless steel with chrome plated surface, wear-resistant and durable. The precise machine structure is equipped with a locking device and makes reading more intuitive and convenient. The built-in ratchet stop device ensures accurate, repeated readings. Technical data: type: internal micrometer measuring range: 5 mm ~ 30 mm material: stainless steel precision: 0.01 mm weight: approx. 9 oz Zero Position: clean the surface of the measuring anvil heads with a soft cloth and then rotate the gauge to get two measuring surfaces contact. If the two zero lines of the differential sleeve and the fixed barrel do not match, use the following two methods to adjust. Method I:If the error is less than 0.001" (0.02mm), use the ratchet stop to lock the screw tightly, and then use a wrench to tighten the fixed barrel until the two zero lines are aligned. Method II:If the error is greater than 0.001" ), Step 1:Use the ratchet stop to tighten the screw, then loosen the ratchet stop with a wrench and remove the differential sleeve. Step 2: Re-align the zero lines of the fixed cylinder and differential sleeve, and then put the ratchet stop back in. Adjust it again with Method I if necessary. Note: No calibration of the micrometer is required under normal use. Micrometers only need to be calibrated when they are severely worn. Package Content 1 x Internal Micrometer, 1 x Wrench, 1 x Calibration Ring, 1 x Packing Box Note: Please note that the new