Thread plug gauges (Item 890) and thread ring gauges (Item 891). In high wear-resistant steel-chrome alloy. Core-hardened, tempered and stabilised. Normally constructed gauges for the following thread types: Metric, Withworth, Cylindrical gas, Conical gas, Acme, American unified UNC, UNF, UNEF. The thread plug gauge is supplied to tolerance 6H and the ring gauge to tolerance 6g in the standard versions.