Firestone TZ300a is a summer tyre made in total of 13 sizes, ranging from R15 to R15 - this particular dimension is R15, which means it fits to a 15 inch/381mm diameter wheel. 185/60 R15 is 10mm wider than the narrowest dimension (175) and 10mm narrower than the widest one (195). This tyre profile of 60 means the sidewall height of the tyre is 60% of the tyre width (185mm), which results in 111mm sidewall height. In 185/60 R15, there is only one possible speed index for Firestone TZ300a - "H", which is good for speeds up to 210 km/h. In 185/60 R15, TZ300a usually competes against Ventus Prime3 K125, which is a tyre from Hankook with a rating of 52%, compared to 0% of the Firestone in question.