- small bag for all your essentials that you want to access easily
- waterproof bag with roll-down closure
- about 2 liters (1/2 gallon), diameter 115mm (4.5") x 215mm (8.5") tall (closed)
- bag can be locked to the holder with a small padlock to prevent
  a "grab-and-run" of the entire bag
- can be mounted on the rear side of your panniers, or somewhere else
- bag weighs only 80 grams (3 ounces)
- spare straps and bags available

Top of bag must be rolled down at least 2 times to achieve waterproof seal.
  
Bags with roll-down closure are not suitable for prolonged submersion. Don't use as a flotation device.