A crawler is a crane mounted on an undercarriage with a set of tracks (also called crawlers) that provide for the stability and mobility of the crane. Crawler cranes range in lifting capacity from about 40 US tons to 3500 US tons. Crawler cranes have both advantages and disadvantages depending on their intended use. The main advantage of a crawler is that they can move around on site and then perform each lift with very little set-up, as the crane is stable on its tracks with no outriggers. In addition, a crawler crane is capable of traveling with a load. The main disadvantage of a crawler crane is that they are very heavy, and cannot easily be moved from one job site to the next without significant expense. Typically, a large crawler must be disassembled and moved by trucks, rail cars or ships to be transported to its next location.