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Terzot Take that measurement again but when the paper is overlapped, draw a line on the overlap so that both ends are marked. Then measure the flat piece of paper between the lines. The results are unexpected for either Columbus or Reynolds, IIANM (If I Am Not Mistaken). Columbus SL had a seat tube of 25mm which yields a circumference of 78.5mm. Paint and decals would not make up the difference to get to 90.5 or a dia. of 28.82.