The cylindrical and conical NRV element, the ring and the pipe segment are auxiliary geometries in order to be able to map the pressure loss of a non-return valve with the simplest possible input parameters.
The values for the length $L$, the flow length $L_{st}$, which can also be longer than the length $L$, the outer diameter $D_A$ and the inner diameter $D_I$ must be specified in the mask for the ring segment.