With flanges bearings, it is easier to fix them to the bearing holes. If you use bearings without flanges, installed into the bearing hole, but also need to be fixed left and right so as not to slip out of the bearing hole; and edge bearing, because one side of the edge, do not need to worry about sliding out of the problem, if you install the wheels, the wheels themselves play a role in jamming left and right, left and right do not need to worry about sliding out of the problem.
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