Product review (1 stars): Shorter than 8 ft, tears easily and not rigid at all.
The duct arrives is a compressed state; in this state is is sufficiently rigid. I tried to extend it to 8 ft length (this is the specification length) by gently pulling the ends apart. It extended to 80 inches (or 6 ft and 8 in) without damage, however, at the 80 inch length it is not rigid at all. It is not more rigid than a foil candy wrapper. When I tried to extend it beyond 80 inches, it just tore apart, or "unwinded" as another reviewer stated it politely. This "unwinding" is irreversible, therefore I had to throw this duct away. Now I am looking for another flexible 5-in by 8-ft duct.