The All Terrain Robot Wheel 130 x 60 mm (Sold as 4) comes with a 6 mm hole mounting brass hub for gear motors. Big diameter all-terrain wheel for explorer robots and land rover robots. The rubber side is semi-pneumatic which means can be squished. It adds an extra dampening factor to explorer robots. Recommended for 10 to 15 kg robots. (4-wheel usage recommended). These large (130mm-diameter) wheels can be used as replacement parts or for custom robots that need to traverse complex, rugged terrain. The black tires are made of soft, spiked rubber for increased traction.