The Ortlieb Back Roller is an easy to use pannier for your bike's rack. The material is 100% waterproof and all seams are sealed for complete water protection. The bag can be mounted on either side, and if you so wish you can buy another one later on. - QL2.1 mounting system holds the panniers securely; the panniers do not simply hang on the rack - Roll-up closure - Quicklock and well adjustable attachments - Shoulder strap - Flat inner pocket with zipper - Reflectors - Welded seams - Five year guarantee - Made in Germany - Main material: easy to clean, tarpaulin-style PD 620 - Bottom and side material: more supple, still highly durable PS 490 Volume: 20 liters, if the mouth of the pannier is rolled enough to keep them waterproof. You can gain extra space at the cost of water protection by rolling the top fewer times.