The width of each trolley is adjusted by rotating the center rod with lifting eye clockwise or counterclockwise. Once the hoist (not included) is attached, the threaded rod in the center cannot rotate which secures the trolley from adjusting accidentally. Each trolley includes 4 sealed rollers with bearings. The lifting eye is located at the bottom of the trolley for easy hoisting access. Trolleys are made up of steel construction and have a painted finish.