European copper tube and fittings
EN Standards have been written to harmonise standards for copper tube and fittings across Europe. This means that products from different manufacturers can be used in the same plumbing system as they all have standardised dimensions.
EN 1057 Copper and Copper Alloys. Seamless, Round Copper Tubes for Water and Gas in Sanitary and Heating Applications specifies the requirements for copper tubes from 6mm up to 267mm diameter: