Nathan VaporKrar 4L 2.0 Race Vest

Backcountry.com says:
You can't stand bringing water with you on a run, but when you're running a summer ultra even you can admit that your stubborn minimalism needs to take a trip to the back burner. For seriously long runs from humid Northeast forests to scorched desert dirt, put on the Nathan VaporKrar 4L 2. 0 Hydration Vest to make sure you stay safely hydrated through your most challenging days. Depending on the length of the run you're prepping for, you can choose to fill the included 20 oz soft flasks with water, as well as add your own 1. 5-liter hydration bladder for extra reassurance. The design focuses heavily on maintaining a breathable, shirt-like fit that won't slosh and bounce for hours on end, so don't feel like you need to skimp on water to preserve your sanity. The soft flasks also come with extended straw tubes so you can sip without removing them from their pockets. Even though you'll have friends waiting with more exciting junk food at aid stations in your race, having a store of easy-to-access energy gels is crucial when you're training, and the VaporKrar's wealth of pockets give you plenty of room to stash as much as you need.