Review on Waterproof Bike Seat Bag by ROCKBROS, 3D Shell Saddle Bag for Mountain and Road Bikes - Cycling Seat Pack Under Seat by Mike Sutherland

So far so good. No comparison with similarly expensive products. Pros: no wobble, 9/10 water resistance, plenty of room A small amount of water will leak through the pocket and zipper - no big deal, just apply some wax or waterproofing spray. It fits a multi-tool, a spare tube, other tools and a granola bar. Cons: Concerned about the silicone mount. Attaches the bottom bag to the seat post. Comes with an extra strap in case one breaks. Eventually it will likely oxidize and break down. Don't worry - if it breaks, the bag can hang on Velcro straps. It would be easy to create your own group.