ISO 4065:2018规定了热塑性塑料管道的公称壁厚en和公称外径dn之间的关系。 ISO 4065:2018适用于沿管道整个长度具有恒定圆形横截面的实壁热塑性管道，无论其制造方法、成分或预期应用如何。 注沿管道全长具有恒定圆形横截面的管道通常称为具有光滑内外表面的管道。

ISO 4065:2018 specifies the relationship between the nominal wall thickness e_n and the nominal outside diameter d_n of thermoplastics pipes. ISO 4065:2018 is applicable to solid-wall thermoplastics pipes of constant circular cross-section along the whole length of the pipe, whatever their method of manufacture, their composition or their intended application. NOTE Pipes with constant circular cross-section along the whole length of the pipe are commonly known as pipes with smooth external and internal surfaces.