Challenge fango tubular cyclocross tyrepros choice for perfect traction in wet muddy conditions all tubular and open tubular produced by challenge are special products machines are not able to produce them and the manual skill required in each step to obtain a good quality standard is very high the casing is produced with the latest technical materials like corespun a cotton and polyester combination corespun is a thread from which we obtain a very supple and strong casing with low weights