Yes they are a variation and where intended for asphalt (and excelled). Testing showed they did work on carpet but were not quite the same or as good as the blue/green. Over a year later we sent some more out for a re-evaluation and there was a few instances where they seemed to work well. As in all things nothing is certain. I still contend it's a particular type of conditions or way in which all the stars must align for these to be the best choice on carpet.

Monti