The Sunlite RackPack Bike Bag with Panniers in the large size drops to $46.93 at REI.com. Even with $5.99 shipping, that's $51 off the original price and beats the next-best price on Amazon by $17. The bag straps into your bike and offers 5 zippered storage compartments with 2 side pockets that expand into large-sized panniers. Plus, it has bungee cords on top for additional storage. It measures 13.4 x 8.7 x 7.9 inches. You can save on shipping costs by padding your order with a small item like this Sunlite TL-L210 Griplite Bike Taillight, reduced from $9.99 to $4.93, to top the $50 minimum. Sales tax is charged in most states.