A great alternative to panniers or a backpack. Ideal for mountain bike overnight trips, but also works will for commuting or long day trips. Outpost Waterproof The included welded stuff bag will keep all your critical gear dry Expandable Sometimes you need more space, while other times you need less. This bag expands to accommodate both. Bag Fit Bikes come in a lot of shapes and sizes. This bag includes adjustable mounting systems to allow fitment to almost ANY bike.