The removable laptop sleeve is designed to protect a standard 15.6-inch laptop computer. It features a key loop and a variety of pockets for small items. It has a fold-over & Velcro closure. The outer shell seals with first a water-resistant zipper, and then a rainproof roll-seal and Velcro closure, and finally a Storm-flap with side-release buckle. On the back of the bag there are ergonomic cushion pads to protect your back. There's also a lash-tab for attaching your bike light. The whole thing weighs only 22oz / 623g. Super-light but super-strong.