The Ortlieb Saddle Bag Two is a lightweight bike saddle bag is constructed from polyurethane-coated durable nylon fabric. Since the material could actually stand up to a good ride ORTLIEB knew it couldntradet go to waste. Since every bike is different and unique the Saddle-Bag Two comes in two different sizes. The 1.6 liter is perfect for those last-minute essentials like an extra snack or rain jacket to keep you comfortable on your latest adventure. The 4.1 liter is ready for the more pre-planned packing like a tool kit plus a sleeping pad when spending the night under the stars.