The HWE folks try to capitalize on the -idea- that bonnet and related cleaning types only clean the top
-third- of the carpet. I see this claim online frequently. That's not what I have observed, however.

On nylon pile carpet, especially the type that is similar to strands of knitting yarn, I would say that the challenger reaches 3/4 of the way or maybe even 9/10 of the way down the fiber. On tightly wound berber carpets, it doesn't do as well, but it cleans at least halfway down the loops. Its hard to tell how much further down it cleans. If you scrub for a long time, I suspect it reaches better than 1/2 way down.