I'll measure up. I seem to remember the piece that went onto the tyre was a sort of spiraly piece of metal? I'll come back to you tomorrow. I bought some Continental Travel Contact which were guaranteed and if punctured they replaced tyre and tube. The front one collected a drawing pin. Shoudda bought a pair of Schwalbe Marathon + - hence the interest in yours. I do also have a classic Cycles Gitane lightweight ladies tourer, flat bars, which has 23 x 700s and this gismo might just protect on the rear wheel which I cant reach to brush off rubbish.