1 1/2 inch-11 1/2 NPSM 2A GO & NoGo Double ended Setting Plug made specifically for setting and checking the wear of NPSM ring gages of the size specified. Use to check the functional fit (feel) of your rings or to set PD on split rings when calibration checks are run./NG RING GAGE Class X NIST traceable Tool steel RC 60/62 (cold stabilized) shipped in polly bag certificate of accuracy with each ring Certificate of Accuracy is included.Click HERE to read about additional Long Form Cert.