At 52.6×107 inches and under 1,000 pounds, the Mule 610 4×4 is the first four-wheel drive utility vehicle small enough to fit in the bed of a full-size pickup truck. The 610 and the two-wheel-drive 600 replace the Mule 550. The 401-cc single-cylinder engine in the 600 Series is 40 percent larger than the 550's. The new vehicles can carry 400 pounds of cargo and tow 1,100 pounds (22 percent more than the 550). The 610 lists for $6,999.