INSIZE Metric Thread Ring Gages, GO - NO GO Set These Metric Thread Gages allow you to inspect the pitch diameter for threaded products. All stock Metric Thread Ring Gages are made to Class 6g per Standard ISO1502. A Manufacturer's Inspection Certificate is included with each gage. Each Metric Thread Ring Gage is marked with nominal size, class of fit and Go or NO GO. Select Thread Size from Pull Down List.