The tubes were ordered from this company.
http://fortecarbon.com/
I have seven two foot sections. The tubes are 2 1/4 inches outside diameter, and just under 2 inches inside diameter. I opted for 2 foot sections because I often travel by plane and wanted to be able to fit them in a suitcase if the need arises. I don't need a 25 or 30 foot rig because I don't bother doing rig shots with lots of space. Most of the rig shots I do are for magazine covers, the cars have to be prominent, so no need for any more sections. having said that, I do plan on getting perhaps an 8 foot carbon section at some point.
They are joined together by aluminum inserts that I had custom machined. The inserts couple together. A friend has the same type of carbon tubes, however, his are joined by aluminum tube inserts that get pinned together.
As with any rig there is some flexing, I use a ratcheting tie down to stiffen the rig. Also, I don't mount the suction cups to anything but glass. I will not put suction cups on anyone's paint or carbon fiber panels.