For zero setting of inside micrometers, three points internal micrometers and bore gages.
Deviation is the difference between the ordered size and the size marked on the setting ring when supplied.
For example, the ordered size is .2”, the size marked on the setting ring when supplied may be .20008″.

Insize 4120-20, METRIC THREAD RING GAGE, GO, M20x2.5, 6928640341519
3M 54135, Scotch-Brite Roloc AL Surface Conditioning Disc TR, 2 in x NH A VFN, 7100075708, 200 per case 