Due to the development history, not all guides had been designed according to the same principle. This has now been implemented with a fundamental adaptation to one design principle for the entire type 441 with bellows for all nominal sizes from DN25-DN400. From now on, the bellows guide will be uniformly provided with a vent hole.

The revised guide can be used 1 to 1 instead of the previously installed guide. The new guides are available as spare parts for maintenance and repair. Existing guides can still be used. However, the new part numbers should then be used for stock management. When using bellows conversion kits, the previously available conversion kits can continue to be used. The newly delivered bellows conversion kits are equipped with the new guide.