Product Description Setting Rings can be used to set Dial Bore Gauges, Holtests, the inside of Micrometers, and other bore measuring instruments accurately and quickly. All setting rings are engraved to 0.0001mm with the actual calibrated size. When selecting a measuring ring, please choose one that is closest in size to the dimension to be measured and that falls within the measuring range of your instrument. Key Features - Used for zero setting of Inside Micrometers, Three Points Internal Micrometers and Bore Gauges. - Durable alloy steel - Hardness of 62HRC - Housed in a protective case Specification -Metric Setting Ring -Size: 25mm/Accuracy: 0.0015mm -Cylindricity: 0.0010mm