The gravel grinder pro open tubularclincher 700c tyre from challenge is designed specifically for gravel racing and features the pps 2 double layer puncture protection strip for added protection against sharp objects the knurled tread helps you to roll faster whilst the deeper and more spread out side knobs help you grip the corners this clincher tyre is moulded using a nylon casing and is suitable for rims 17 23mm wide available in 700 x 36c black only