LightRail® offers a suggested upgrade item for moving multiple lights with one motor or heavier lights weighing 35 lbs. or more. The Extreme Duty Trolley Wheels are engineered with steel on steel ball bearing, with a nylon over-molded tire for smooth and quiet operation. They come four wheels to a package and are rated to 60 lbs. per set. They are compatible with LightRail® 3.5, 4.0, and 4.2. The Extreme Duty Trolley Wheels come with a lifetime warranty.