Knorr-Bremse in the past has made it hard to work with their part numbers (my opinion), just think about part number / type number issue or simply compare with Wabco.
Partially this is consequence of the fact that Knorr has acquired air-brake divisions of Robert Bosch, Magneti Marelli, Bendix, Paul Dahl and they had to integrate all those references to their database. Not an easy job, I admit.
In August, 2007 they introduced a new approach to index their part numbers which now refers to 4 main properties of the product.
How does it work?