Seam welded, to keep water out and provide maximum protection for contents. Constructed from high quality, waterproof materials and optimized for durability and weight. Designed to make full use of the space under the saddle, eliminating the need for a rear rack. Performs best when used to carry lightweight, compressible gear, such as clothing or sleeping gear but built super strong to handle other loads as well! This Pack has been designed to keep water out, even in a sustained rain. The product features a hassle free air release vent and is therefore not submergible.