Ideal Security's steel garage rollers are replacement rollers for residential garage doors. These commercial grade steel wheel rollers are extra durable and higher quality than the standard OEM rollers included with most garage doors. Ten ball-bearings per wheel reduce rotational friction between roller and shaft and provide a smooth opening and closing of your garage door. The 2-inch wheels fit 2-inch tracks, the residential standard. Stems measure 4-inches for standard single-hinge installations.SK7171 package included ten rollers. The average residential garage door has 10 rollers on it. For smooth and easy opening and closing, and to extend the life of the electric door opener, change all rollers at the same time or when adding a new electric opener. For hinges, consult the SK7101, SK7102, and SK7103 from Ideal Security.