Well, Amram, the problem I ran into with one of the commercial versions, it was made of high tensil plastic. almost like a heated plexiglass material and it broke in several places. It only lasted me a few weeks! I bought a different model from a different company and, so far, so good. But, I kept the broken parts of the old one to make one out of 1/4" plywood.

Good luck with that. When used properly, as I am sure you know, they are most comfortable.

DS.