The Challenge Grifo tubulars are the tires that set the standard in cyclocross. Challenge tubulars are handmade tires with super supple sidewalls (similar to Dugast tires). Need tubulars? The Challenge Grifo are the ones you’ll want to have. The NEW Grifo Team Edition S features a pre-sealed 320 TPI Cotton casing, tread is glued onto fully-inflated casing to achieve a neutral tread state when tires are in use. 40mm valve stem and 405 grams. Absolutely no tubular may be returned that has been glued.