I have one that measures 19" on the outside. I used to use the regular thin ones, but after breaking so many of them, I built my own. I took pieces from 3 of the ones that I broke and created this. I doubled the outside rings and taped them together with black electrical tape, (the only tape I had at the time). Then I doubled the inside rings and taped them together with white electrical tape. The rings are about 1/2" thick now.
It works for me, and I have used this for about 14 years with no problem, (ever since I broke one of the boards to my floor frame).
I tried one of the square snap together ones, but I didn't like it. So, when and IF i break this one, I will buy 3 new ones and make another one exactly like this.
Last edited by cad_queen_2000; 10-21-2012 at 11:33 AM.
Reason: spelling