I don't know if anyone is doing any HVAC projects but I just finished mine and have some left over ducting material.
(2) boxes of 5" x25' flex duct R4.2
(1) box of 6"x25' flex duct R4.2
(1) box of 12"x25' flex duct R6

I have it on the CL for $50 for everything, NESR discount will get you to $40. These are all new unopened boxes. I'll even throw in 1/3 of a tub of mastic that I have left over.