Not only is the Marathon Vest V2 an amazing hydration solution for runners, it even comes with 2 Flexform™ II 300 bottles so you have everything you need to run your first ultra. Fully adjustable, with a large back pocket that holds up to a 2 liter reservoir, it also has plenty of other pockets for storing the many important things you may need on your run. Comfort glide back adjuster system for full body adjustability Comes in 2 sizes for customizable fit Comes with 2 Flexform™ II 300 bottles so you have everything you need to run your first ultra Large back pocket can hold up to a 2 liter reservoir 2 rear pockets, 2 lat pockets and 5 front pockets provide plenty of storage and organization 1 secure zippered pocket at front for storage of keys or valuables Bottles Included: 2 Flexform™ II 300 Weight (Without Bottle): 136 g / 4.8 oz Volume: 5.41 L / 330 in3 Length: 15 in Width: 12 in XS/SM: 53 - 102 cm / 20 - 40 in MD/LG: 76 - 117 cm / 30 - 46 in Composition: Perforated polyester plain weave, 80/20 nylon spandex stretch mesh