Vredestein ULTRAC is a summer tyre made in total of 48 sizes, ranging from R15 to R15 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 305/30 R20 is 130mm wider than the narrowest dimension (175) and -10mm narrower than the widest one (295). This tyre profile of 30 means the sidewall height of the tyre is 30% of the tyre width (305mm), which results in 91.5mm sidewall height. In 305/30 R20, there is only one possible speed index for Vredestein ULTRAC - "Y", which is good for speeds up to 300 km/h.