R:Loop. According to the site these bands will stretch to 10x their resting length
6 inch and 10 inch diameter continuous loops http://www.re-designonline.com/#
Wow, that stuff looks absolutely incredible!
Not cheap though, you probably need at least 3 aside, $78, p&p...
But still tempting, very impressive stuff, great grip, no knot or plug, easy grip, and then most and for all that 10-12x resting length, this should give far more flexibility then other strands. Wonder if their action is reasonably linear?