A tractor unit can have many axles depending on axle load legislation. The most common varieties are those of 4×2, 6×2, and 6×4 types. However, some manufacturers offer 6×6, 8x4, 8×6, 8×8, 10×8, and 10×10 axle configurations. A 6×4 has three axles, normally an undriven front steer axle and the two rear axles driven. 6×4 units are more common in long-distance haulage in larger countries such as the United States and Australia. In Europe, the 4×2 and 6×2 variants are more commonplace.