Quick Slicks CA21 tires are designed specifically for 1:32 Carrera Porsche 917K stock (plastic) wheels.
For a complete list of cars/wheels this tire will fit, please refer to the Quick Slicks Fitment Summary which is updated on a regular basis.
Multiple silicone compounds are available - this is the X-FIRM compound (part number: CA21XF).
Outer Diameter (O.D.): .841" (21.35mm)
Width (Contact Patch): .490" (12.44mm)