What does the designation sch20 mean? What are SCH20-SCH40-SCH80-SCH160? Friends who do foreign trade often ask questions like, ‘ASTM A106 Gr.B, 12, SCH40, 6m, SML, API 5L Gr.B, 12, SCH40, 6m, SML’ What do these mean? The steel pipe size given by the customer is in British system, how to convert it to metric MM? What are the outer diameter, inner diameter and thickness of the steel pipe? Let’s take a look at what SCH20 means today?