10pcs/lot Hex Coupling Hexagonal Tire Connector 2mm/3mm/4mm/5mm/6mm/8mm Shaft Copper Connector for Motor Wheel Robot Car Chassis
https://www.vogueparade.com/shopping/EN/200001385/1/1005001872191483/10pcslot-hex-coupling-hexagonal-tire-connector-2mm3mm4mm5mm6mm8mm-shaft-copper-connector-for-motor-wheel-robot-car-chassis//