Revelate has set out to develop the most stable, flat, and feature-rich waterproof seat bag on the market. The Spinelock incorporates customer-tested and proven features such as a one-way valve, taillight slots, loop and bungee deck, and an external plastic bottom with a patented attachment system. Stability was the driving factor in the design process. If you're looking for something you can pack and forget, the Spinelock is your seat bag.