What makes the Ortlieb back roller panniers so great? Here are some of the key features and benefits of this top-notch bike bag. One of the biggest selling points of the Ortlieb Back Roller is its waterproof design. Made from tough, durable PVC-coated polyester, this pannier will keep your gear dry no matter how wet the weather gets. And because it's built to last, you can count on it to hold up to years of heavy use.