One client ordered:

BSPP G1/8 x 28 thread plug gauge GO & NOGO with calibration certificate US$75

However, client’s quality team is thinking they got just the G1/8 (shown below):

BSPP G1/8″ thread plug gauge GO & NOGO US$40

Did they receive wrong item? no, they received correct item

28 is the TPI (Thread Per Inch), For G1/8, the TPI28 is constant. so it can be marked out, it also can not be marked out. Both is correct.