This type of crane style gives the highest possible hook height and the highest capacity depending on your needs. Usually a double box girder top rider crane is slated for of up to 50+ tons capacity. It is called a Box Girder, because instead of the normal I beams on the bridge, this crane's bridge is made out of a box. The box structure can withstand more tension, and rotating forces, allowing for some of the largest load capacities of all overhead cranes.