Apollo Alnac 4G Winter is a winter tyre made in total of 20 sizes, ranging from R13 to R13 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 255/40 R20 is 100mm wider than the narrowest dimension (155) and -40mm narrower than the widest one (215). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (255mm), which results in 102mm sidewall height. In 255/40 R20, Alnac 4G Winter usually competes against Snowpower HP, which is a tyre from Tristar with a rating of 0%, compared to 0% of the Apollo in question.