American National Standard Gagemakers Tolerances
ANSI B4.4M-1981 (R1994)

a Gagemakers tolerance is equal to 5 per cent of workpiece tolerance or 5 per cent of applicable IT grade value.

All dimensions are in millimeters.
For closer gagemakers tolerance classes than Class XXXM, specify 5 per cent of IT5, IT4, or IT3 and use the designation 0.05 IT5, 0.05 IT4, etc.

Relationship between Gagemakers Tolerance, Wear Allowance and Workpiece Tolerance