O.K....I thought it looked like they were using 16" or something. The high step I got said the platform was 4 1/2", and the risers two inches.
I used to use 14" when using tall box work before (used the firm box), I did step ups yesterday with this box (not a particular workout, just doing them while watching the boob tube) and I had many pros and cons at this height. I am 5'4", so I was just a tad shy of being parallel. I really concentrated on putting my weight through the heel, and found that I could perform more reps, but didn't seem as challenging. However, I'm sure once I do a true workout from a dvd/video, it will be perfect at this height. Oh well....experimentation, experimentation, experimentation!!! ;-)