Functions and Usability These Jonex Tenacity Quad Roller Skates can be used by both junior and senior skaters who are above the age of seven and skate for recreation. The frame of each skate is made of steel for sturdiness and the steel ball bearings ensure ease of movement. Benefits and Safety Features The quad roller 55 mm wheels of each skate are made of rubber and come with brakes to ensure that you can stop exactly when you feel like. We kept the weight to an absolute minimum without sacrificing safety, through our reinforced design.