Transition sections are used for the connection of different nominal sizes. The socket is always at the smaller diameter side. The transition sections respect the continuity of invert.
Vitrified clay pipes and fittings are standardised in EN 295-1. Supplementary requirements defines the certification program ZP WN 295. All measurements - especially when connecting to other products - must be checked and depend on the specifications of EN 295 and on the certification program ZP WN 295. Subject to technical changes.