Designed for Boost E and Carry On. Sold separately. Our large capacity pannier bags are designed to carry a variety of different loads, big and small. The adjustable strap system lets you secure anything from boxes to oversized items by simply tightening the horizontal and vertical straps. Depending on the size of the item, you can either close the cover or roll it up and fasten it with a Velcro strap to allow extra room for the load to extend out.