Abrasive materials.  It's a relatively new subject for most with the Ultimaker S5 and the (soon to be released) print core CC Red. Adding to that, Ultimaker is working close to various material manufacturers to include validated profiles from their materials into Ultimaker Cura as well. So, as a user, you are can rely on the same reliability as when you use Ultimaker materials, but with possibly enhanced properties.   Some of these enhanced properties come from the additives