GoodYear UltraGrip Performance+ is a winter tyre made in total of 176 sizes, ranging from R15 to R15 - this particular dimension is R21, which means it fits to a 21 inch/533.4mm diameter wheel. 255/50 R21 is 60mm wider than the narrowest dimension (195) and 20mm narrower than the widest one (275). This tyre profile of 50 means the sidewall height of the tyre is 50% of the tyre width (255mm), which results in 127.5mm sidewall height.
Winter
Winter
Winter
Winter