This is a DFRobot designed black rubber wheel kit. The custom-designed kit contains two 136mm rubber tires tested over 6 indoor conditions,packed with shaft couplings, two M8 screws and 2 washers. Designed to fit on DFRobot HCR(Home Care Robot) platforms and other indoor mobile robots, the dent on the wheel has a good anti-slip effect and provide a firm grasp over the moving surface. Our tailored couplings is your best choice to consider,but you can also use your own couplings.