Product Description Metric screw ring gauge is a gauge used to test a threaded shaft. The Go gauge must be able to be screwed on the threaded shaft without excessive force. The No Go gauge must not fit on the test item. These gauges are ideal for determining whether the actual thread of a test item is within a specified target range. Made from hardened alloy steel for longer tool life and durability from machine shop wear. Key Features - High quality hardened steel for durable tool life - Fine ground screw threads - Can identify either GO or NO GO Specification -Metric Coarse Screw Ring Gauge, ISO 6g, No Go -Size (mm) : M30 3.5