Racing wheels are basically classic wheels for in-line skates. The difference is that for speedskating are wheels bigger, more expensive and of high-quality. Rules for choosing hardness are the same as for classic wheels. Harder wheels are faster and last longer. Hardness is marked with number and letter A or F. On A scale - the higher the number, the harder the wheels. On a F scale it is the other way around. For example hardness 86A is harder than 80A and F1.