This nylon hydration backpack has a 15 liter main capacity plus a 3 liter PEVA water bladder that is BPA free. The bladder sits in an insulated compartment that keeps drinks cool for up to 5 hours, with a kink-free sip tube, a push-lock bite valve and a 2 inch opening for ice and cleaning. It has three zippered compartments, two side mesh pockets and two waist pouches, with mesh padding on the straps and back. It measures 11 by 3.9 by 18 inches.