The dimensions z, a and e are reference values. Other dimensions and crushing strengths: see pipes. The strength class of the branch piece is always normal strength.
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.