Thule Rail 4L is a smartly designed hydration pack that keeps you hydrated without missing a moment on the trail. The Thule ReTrakt Water Bladder Tube has a unique magnetic design that allows the tube to automatically snap back into place between uses, so you stay hydrated without taking your attention off the trail. This hydration pack also offers superior stability and breathable materials that ensure comfort and the reflective elements and bike light attachment loops offer visibility at night. Easily access your phone with one hand while on the bike, and stash tools and snacks in organized internal pockets. This hydration pack is a perfect addition to your 1-3 hour runs.