Also dirt bikes are considered to be ATVs as that they were designed for off-road use only. Although most are equipped with three or four wheels, six-wheel models exist for specialized applications. Engine sizes of ATVs currently for sale in the United States, (as of 2008 products), range from 49 to 1,000 cc (0.049 to 1.0 L; 3.0 to 61 cu in).