Typically major brand inline skates like Rollerblade, K2 and Salomon will print the maximum size wheels that the skates will fit somewhere on the frame. Usually this is shown as "Max wheel size, XXmm" where XX is the maximum wheel size that is recommended for your skates (example: Max wheel size, 90mm). In the case of a roller-hockey skate that may use more than one inline wheel size look for something like Hi/Lo 72/80 or 72/76/76/80 on the frame. In the first case 72/80 is telling you that that the skates use a combination of two 72mm wheels in front and two 80mm wheels in back on each skate. The second example 72/76/76/80 indicates that each skate uses three sizes, a 72mm in front, two 76mm in the middle and an 80mm wheel on the back.