I may have not understood the discriptions accurately. I have a 1950's seat binder bolt and nut that I believe is original cinelli.It is 10mm, the shaft of the bolt is gradually tapered to a smaller diameter from the bolt head to a mid point in the length of the bolt then tapers back up to the threads for the nut. Is this what we are talking about? The photos look fine but they have no taper. Craig Griffith San Luis Obispo,Ca.