根据BS 66和99、BS 1306和BS 2871:第2部分，与管道和管件一起使用的螺纹，对于BS 21中的螺纹不适用，或由于厚度不足而无法使用。交叉引用:BS 21BS 66和99BS 1306BS 2871:第2部分ISO 7

Threads for use with tubes and fittings to BS 66 & 99, BS 1306 and BS 2871:Part 2, for which threads to BS 21 are not suitable or cannot be utilized due to the thickness being insufficient.Cross References:BS 21BS 66 & 99BS 1306BS 2871:Part 2ISO 7