The use of NB, KT or LINA in variable names is not allowed.

Also do not use the variables NN, NT, VARIANT, VARSET and VERSION as these can also cause problems.

When assigning variable names, the same scheme should be used the same scheme. For example, do NOT use "L" and "L1" for the length of two similar products.

This is particularly relevant for the facet search, among other things, so that a variable filter can really output ALL relevant products.