These are some shots of my latest toroid, a 7" x 26.5" one, made with semi-rigid ducting. The center hub is made from two cake pans from Big Lots(a dollar store type place). I screwed them together with four #6 machine screws. The seam isn't too ugly and I'll probably cover it with a piece of aluminium tape at some point for asthetics. This toroid is for my new 4" coil.