I bought something like this 15 years ago at a WHOLE LIFE EXPO here in SF. I used it for a couple hours and found it strained my knees. Turns out another Rolfer saw this in his practice also.
These things sheer the tibia and strain the posterior cruciate ligament almost as badly as the Blaans chair. Stay away from them and learn to sit on your sitz bones and feet by just tilting your chair forward a bit.
