This ultra-lightweight women’s specific hydration pack is ready for anything from a recreational weekend trail run to the most aggressive ultra-marathons. Because Nathan tests all their products on professional runners, you know this pack has been approved by some of the best trail running women around. The Airess not only packs a 2-liter hydration bladder but also has two front bottle pockets, a mesh pocket that holds several gels, an easy-clean pocket to hold empty gel packs, 4 rear gear attachment points, a water resistant pill pocket, a smart phone compatible pocket and an additional 5-liters of storage not counting the bladder. If you’re thinking this sounds like a bulky day-hike pack, think again. The Vapor Airess weighs only 9.3 ounces with the bladder.