GAS是英国标准圆柱管螺纹.参考GB 8335-1987 THREADS;SCREW THREADS;GAS CYLINDERS 。

NPT 是 National (American) Pipe Thread 的缩写，属于美国标准的 60 度锥管螺纹，用于北美地区．国家标准可查阅国家标准GB/T12716-1991。
国家标准可查阅 GB/T7307-2001 另外螺纹中的1/4、1/2、1/8 标记是指螺纹尺寸的直径，单位是英吋．行内人通常用分来称呼螺纹尺寸，一吋等於8分，1/4 吋就是2分，如此类推．

Common American National Standard Pipe Taper Threads

NPT - National Pipe Thread Taper
FPT - female (internal) National Pipe Taper threads
MPT - male (external) National Pipe Taper threads
NPTF - Dryseal American National Standard Taper Pipe Thread (ANSI B1.20.3)
For NPT threads a sealant compound or Teflon tape must be used for a leak-free seal. For NPTF
no sealant is needed for a sealing.

Characteristics of NPT (also known as ANSI/ASME B1.20.1 Pipe Threads, General Purpose):

tapered thread 1o 47'
truncation of roots and crests are flat
60o thread angle
pitch is measured in threads per inch