Nathan VaporAiress 7L

Backcountry.com says:
The Women's Vapor Airess Hydration Race Vest is Nathan's lightest vest for runners who don't want to be weighed down. This women-specific vest features super breathable materials that are body-mapped for the utmost comfort. Over-the-shoulder load lifters pull the vest close to your body for bounce-free convenience. Nathan included a 2-liter bladder with a quick release valve for easy drinking, and there are two front pockets for extra water bottles. The Vapor Airess also features two front stash pockets, a water-resistant pocket, and side stretch mesh pockets that fit most smartphones and cameras. Reflective details keep you visible in low light.