8-32 UNC Class 2B & 3B Special Go plug member only (no handle included) used to check threads that will receive STI or Helicoil inserts. Tool steel cold stabilized Rc 60-62 light blue optional handles for inch yellow optional handles on metric plugs. NOTE: selection of a 2B or 3B is based on your requirements. a 2B or 3B only effect the pitch diameter of the NoGo plug with a 2B class providing a larger PD on the plug gage. Certificate of Accuracy is included.Click HERE to read about additional Long Form Cert.