I'm puzzled as to why Jon's message shows "thingyblick" when I put it in quotes to respond the address comes up correctly, "Ricard Blick Art Supplies."
Since this is a "family" BB, the 4-letter nickname for "Richard" shows up as "thingy".
When I first saw Jon's response, I reached back into the recesses of my public school supply purchasing experience (retired 2 years ago) and thought, "Hey, that is the old Richard Blick Art Supply Company. Sure enough, when I put in [www.(put in 4-letter nickname for "Richard" here)blick.com] the right website came up. ;D
Jon is correct, $4.85 per running foot, 24" wide in a variety of colors.
Mike, you will need to attach something to the corners of the AC vent that is made of iron so the magnetic material will adhere... shouldn't be too difficult if you find a sheet of galvanized tin and make some 2" squares attached with screws at the corners of the vent. 8)