Michelin Alpin 5 is a winter tyre made in total of 87 sizes, ranging from R15 to R15 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 245/50 R18 is 60mm wider than the narrowest dimension (185) and 70mm narrower than the widest one (315). This tyre profile of 50 means the sidewall height of the tyre is 50% of the tyre width (245mm), which results in 122.5mm sidewall height. In 245/50 R18, Alpin 5 usually competes against Blizzak LM-005, which is a tyre from Bridgestone with a rating of 87%, compared to 0% of the Michelin in question.