The Challenge Grifo tubulars are the tires that set the standard in cyclocross. Challenge tubulars are handmade tires with super supple sidewalls. The Challenge Grifo are the ones you’ll want to have. 300 TPI Super Poly Casing gives supple ride quality in a light 415 gram tire. Now available in 33mm. A perfect match with our Mastik Tubular Glue and and Sidewall Sealant. Absolutely no tubular may be returned that has been glued.