We Recommend to buy  the original DC Motor Driver & Controller for this robot (it sold separately)  Find it Here This 4WD is the little brother of the 6WD Wild Thumper: It takes almost no time to go from un-boxing to rolling chassis, but it's also ready to be expanded on and makes great base for an Advanced Robot. The chassis has wicked spiked 120mm diameter wheels and an anodized aluminium chassis made from 2mm thick plate. The 4WD also comes with a 2DOF Arm. It includes 2x 1.8Kg/cm GWS STD micro servos to operate the wrist and gripper. The chassis has 4mm diameter holes punched every 10mm to allow easy mounting of PCBs, servos etc. All nuts, bolts and screws are stainless steel. Brass fittings and suspension springs are nickel plated.   Specifications: • Aluminium chassis made from 2mm thick plate with • 4mm diameter holes punched every 10mm • Two covered chassis segments to hold batteries and circuitry. • 4x DC Motors (75:1 Gearboxes) • Motor Specifications◦Voltage: 6V (7.5V max) • No load current: 350mA • Stall current: 5.5A • Motor RPM: 10,000 +/- 5% • Gearbox ratio is 75:1 • Output shaft speed is 133rpm +/- 5% • Stall torque is 8.8Kg/cm • Dimensions: 270 x 285 x 130 mm (without clamp) • Tray dimensions: 230 x 120 mm • Battery compartment: 138 x 65 x 38 mm • Wheel Size: Ø125 x 60 mm • Wheel axle diameter: 4 mm • Ground clearance: 60 mm vacuum • Total weight (clip included): 2.15 kg • Degrees of freedom for arm: 2 •All nuts, bolts and screws are stainless steel. Brass fittings and suspension springs are nickel plated.