I have a 10" OD Parallax aluminum tube. It is 48" long. Each end is rolled for strength. The wall thickness is .064. There are three holes on one end at 120 degrees from each other for mounting a mirror cell. I purchased it to build a small dobsonian for a friend. The mirror ended up with a bit longer focal length so I had to order a longer tube.
Parallax's current prices are $34 per foot plus $15 to roll the ends. I'll sell for $75 plus shipping. ($95 previously).