Most of the time you probably won't notice the Castelli Undersaddle Mini but at some point what you put in it will probably will be the difference between whether you call your spouse for him to pick you up on the side of the road or just change the tube and keep riding. No wonder they call it a mini bag so pack everything you need for your trip and leave unnecessary items at home. Noticing a bag under the saddle isn't too bad either - it's made of smooth water-resistant material with Castelli's signature clean lines and classic style and even fastens with a water-resistant zipper to keep your things safe. while showering. Reflective accents make you visible to motorists at any time of the day and the bag attaches neatly and securely to the saddle using a Velcro strap.