Barum Polaris 5 is a winter tyre made in total of 74 sizes, ranging from R13 to R13 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 235/40 R18 is 100mm wider than the narrowest dimension (135) and 20mm narrower than the widest one (255). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (235mm), which results in 94mm sidewall height. In 235/40 R18, Polaris 5 usually competes against Winguard Snow G3 WH21, which is a tyre from Nexen with a rating of 60%, compared to 63% of the Barum in question.