A quad scull, sometimes known as a quadruple scull, is a rowing boat used in competition rowing. It is intended for four individuals who scull with two oars in each hand to move the boat. There are several types of boats that can be referred to as quads. The number of oars per person varies depending on the type of boat. In a coxed quad, one person sits in the bow and steers with an oar in each hand. The others sit in the stern and scull with two oars in each hand. In a double quad, three people usually sit in the boat, with one person rowing in the bow and steering with an oar in each hand, and the other two sitting in the stern and using two oars in each hand. The term "quad" also may refer to the number of people in the boat, without reference to their relative positions. For example, a quad of eight people would consist of four pairs of twins or sibling rows. Quads are typically between 18 and 22 feet long and weigh around 1500 pounds. They have flat bottoms which make them stable on water but not very fast (about 15 miles per hour). There is no specific national body that controls the development of quad racing.