The Schwalbe Extralight No.20 is a lightweight tube for 28'' road bike tires. The butyl rubber tube is extremely airtight and elastic. The high elasticity means the tube covers a wide range of tire sizes.
The Schwalbe No.20 fits the following tire sizes:
18-622 (700 x 18C) 20-622 (700 x 20C) 22-622 (700 x 22C) 23-622 (700 x 23C) 25-622 (700 x 25C) 22-630 25-630 ;
