In addition to the unique new motion fit construction, XT Advanced Skin 5 S-Lab incorporates a wealth of other innovative features. Replacing traditional sternum straps, the Twin Link system is fully adjustable and made from soft, stretchy material, providing flexible adjustability and stability without limiting the runner's motion or breathing. All seams and hard materials in the pack are minimized, completely eliminating chafing and abrasion. The Source hydration bladder hose is routed through the bottom of the pack straps, reducing the hose length so drinking requires less energy. The XT Advanced Skin 5 S-Lab also securely holds a host of Salomon accessories, enabling runners to add volume, carry poles conveniently or attach more water bottles. Finally, an included safety "space blanket " doubles as padding and back insulation for the hydration bladder. But with all these features, the thing that is perhaps most striking about the XT Advanced Skin system is how light it is. There is very little material in the pack, and the material that is there is extremely light and soft. Looking at the pack, one can see it is minimal, but wearing the pack feels about like wearing an extra shirt. There is nothing excessive.