None of the SPEC balls - Crux Prime, Gravity Evolve, and Pro Motion - were too popular. I believe they have all been discontinued too. It's not really a huge surprise given what kind of ball motion those covers dictate. Definitely not something most are looking for on house or even drier conditions.
The Pro Motion was the best/most usable of the three but like mentioned above it's still pretty control-oriented. Not a bad thing, and probably something more should be looking for, but not a seller either. I can't help but think that a better name and less boring color scheme would have helped tremendously.