Runfarr Innner Tube for Super 73,4.00/4.90-20 Tire Tube Replacement Tubes for Electric Bike Super 73 S1/Super 73 S2/Super 73 RXFitment: For Super 73 S1 For Super 73 S2 For Super 73 RX Features: 100% Brand new, never mounted, high quality. The tire tube for Super 73 is made of high-quality nitrile rubber, which has good elasticity and wear resistanc..