The rear-mounted, joystick-operated Manual Wheelchair ZX-1 Power Add-On attaches directly behind the chair-no tools or fasteners reportedly needed. The battery-powered unit can reportedly generate a speed of over 3 mph for up to 5 miles before recharge is required. It fits most chairs 15 to 20 inches wide with wheel sizes 24 to 26 inches in diameter. Standard features include: front and rear drive wheels, twin 24-volt batteries with charging station, battery-level-charge indicator on joystick, pneumatic tires, anti-tilt mechanism, and carbon fiber motor cover. Optional accessories are armrest extensions and off-road tires.