Ironically I just ordered an Airhawk this morning, after much deliberation about size for the XTZ. I went for the Cruiser Small ( http://www.bykebitz.co.uk/acatalog/SMALL_CRUISER.html), which is 18" and 12" wide (at the widest point), but it tapers to 9" at the front and 10" at the back, which by reckoning/measuring will fit the seat perfectly? We'll see when it arrives...

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