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 real 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, and easy-clean pocket to hold empty gel packs, 4 rear gear attachment points, water resistant pill pocket, 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.