Thread Check Inc. offers trilock plug gages in class XX thru ZZ gagemaker tolerances for checking large diameter holes. Like reversible gages, when one side wears out, the gage can be turned around. This design significantly increases the life of the gage. trilock plug gages are made of quality tool steel and chrome for longer gage life. Sizes range from .7600" - 8.010" / 19.30mm - 203.45mm.