Goto Office Depot. They have <=3" Diameter and 33" long tubes to mail Posters etc. in. These are very strong. I tried to crush one with my hands and i couldn't, i couldn't even bend it!! I tried hard too. You can't build a big coil with it. But for a 4 dollar tube, you can't beat it, especially after a few good thick coats of polyurathane.