Same, exact one that JC was using in the video. You can actually get them in different grits. I agree that the Flex Flap is probably still the best bang for your buck.

I saw Jody using a 3M Bristle Disk on his welding cart project so naturally I knew I needed one. Same with Norm Abrams or any of the other DIY helpers. If they use it, you need it, right? I found one on Ebay for $24 including shipping. I made it through about 42 feet of 1" square tubing before ...