The excavation component of a bucketwheel excavator is a large rotating wheel mounted on an arm or boom. On the outer edge of the wheel is a series of scoops or buckets. As the wheel turns, the buckets remove soil or rock from the target area and carry it around to the backside of the wheel, where it falls onto a conveyor, which carries it up the arm toward the main body of the excavator. Additional conveyors then may carry it further; in some cases, several long conveyors are placed end-to-end, each supported by a large vehicular base (usually with caterpillar tracks). Especially large bucket-wheel excavators, over 200 meters long and up to 100 meters in height, are used in German strip-mining operations, and are the largest earth-movers in the world. These tremendous machines can cost over $100 million, take 5 years to assemble, require 5 people to operate, weigh more than 13,000 tons, and have a theoretical capacity of more than 12,000 m³/h.