So if you have rails larger than 7 mm do you need this new clampset maybe maybe not thomsons standard rail clamps can accommodate rails up to 7 x 10mm but riders using their setback post with over sized rails may have issues getting the saddle nose down if this is you the over sized rail clampset will give you about 5 to 8 more degrees of nose down adjustment the over sized rail clampset is also more cosmetically appealing than the standard clamps on over sized rails the over sized rail