Product review (4 stars): Works as advertised
This duct is what you'd expect.  Uninsulated flexible ducting.  The foil is pretty tough for foil and doesn't tear easily.  It is somewhat difficult to cut to length cleanly, but the wire that helps it keep it's shape is fairly thick and stiff and makes this quite resistant to collapse under suction.

I used it to modify a portable A/C unit and had no issues with it.