Comparison : Item # 1/8-27 NPSM Ring Go 2A, 0.3725 Inch (in) External 2A National Pipe Straight Mechanical (NPSM) Thread Ring Gage
Item # 1/8-27 NPSM Ring No Go Class 2A, 0.3689 Inch (in) External 2A National Pipe Straight Mechanical (NPSM) Thread Ring Gage
Item # 1/8-27 NPSM Ring No Go/Go Class 2A, 0.3689 to 0.3725 Inch (in) External 2A National Pipe Straight Mechanical (NPSM) Thread Ring Gage
Item # 1/4-18 NPSM Ring Go 2A, 0.4903 Inch (in) External 2A National Pipe Straight Mechanical (NPSM) Thread Ring Gage
Item # 1/4-18 NPSM Ring No Go Class 2A, 0.4859 Inch (in) External 2A National Pipe Straight Mechanical (NPSM) Thread Ring Gage