The NPT, PT, G thread are all pipe thread

2.The abbreviation of PT is Pipe Thread, 55 degrees sealed tapered Pipe Thread, belongs to the family of wyeth Thread,it main used in Europe and the commonwealth countries. More commonly used in water and gas Pipe industry, the taper regulations is 1:16. The national standards for GB/T7306.

3.G is 55 degrees the threaded pipe thread sealing, wyeth thread family.it marked as G on behalf of the straight thread. National standards for GB/T7307

   In the other thread 1/4, 1/2, 1/8 mark refers to the diameter of the thread sizes, the unit is inch. Inline people usually use points to call thread sizes, one inch equals eight points, and 1/4 inch is 2 points and so on.

   G is generally referred to as the pipe thread (Guan), 55, 60 degrees division belongs to functional, commonly known as round tube. The thread by a cylinder.