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″.

Dynabrade 02445 2 hp Housing Assembly for 53252
Dynabrade 11399 Type 27 Wheel Mounting Adapter Kit 