HYDRAPAK reservoir bladder and drink system included Low profile body hugging design Dedicated bladder compartment with zippered shoulder strap tube adjustment Zippered front accessory pocket for valuables Padded adjustable shoulder strap for maximum comfort. Padded back with air flow channels for ultimate cool comfort 70 oz/2.0L Bladder ? FDA Approved Polyurethane MATERIALS 600D Poly PU2 / 420D Dobby Poly PU2 / 400D Nylon PU2