DESCRIPTION 13mm Aluminum Ball-Race Rollers have excellent durability and are equipped with 520 ball bearings for smooth rotation. In addition, these rollers experience less friction against Mini 4WD course walls and can be used for both front and rear roller setups. This popular Grade-Up Part comes available in special limited-edition red color which you can use to dress up your Mini 4WD machine. • 13mm Aluminum Ball-Race Rollers (Ringless/ Red) x2 • Built-in 520 ball bearings ensure superior smoothness of rotation, for minimal time loss. • Screws and small parts for attachment included. • Compatible with Mini 4WD and Mini 4WD PRO cars set up for use with 13mm rollers.