Thanks guys! The cylinder is just cardboard, but is actually a suggested way to build a sub box, as in the
Car Audio Cookbook. It sure did make it easier to do too. The tube is actually what is used for making concrete columns or footers, so I bought it at Lowe's.
And surprisingly enough, the dash doesn't rattle! I was sure it would, so I was pleasently surprised that it didn't. I even had the foam insulation ready to go in there, but didn't need it!
