I just want to pop in here with a word of caution to anyone considering buying an "original" version of a Skier's Edge (like in a thrift shop or garage sale).
I got one back in 1991 as a partial way to come back from an ACL reconstruction. While the unit provided excellent strengthening, balance, and mobility exercise, the rubber belts on those original models were junk. Maybe I was cycling it more than most people would (I'm 6'1", 195#), but I broke bands regularly. I probably had to replace the bands about six times.
Eventually, I got annoyed, frustrated, etc and threw the whole unit into a pond where it even now provides wonderful cover for largemouth bass and bluegills.
My understanding is that the newer models have solved that problem and I am not complaining about newer models. I just want to warn unsuspecting shoppers out there that the original model will not continue to function very long if you use it hard.