Being isotonic means that isostar is made to match the fluids in your body so it's absorbed faster and hydrates you quicker than water! During sport activity, the body uses large amounts of energy. Fluid & important minerals are also lost thorough perspiration, impairing sporting performance if not replaced. New Isostar Hydrate & Perform sports drink - formula is now proven to boost sporting endurance by 19%* thanks to its Isotonic formula.    *Scientific Study, IRMS, 2004 Each 400g tub makes 5 litres of fluid when mixed with water. Avaailable in orange or lemon flavours. Price £6.79 each or buy a case of 6 tubs for only £38.50 Please email us  at sales@ontherun.co.uk if you wish to buy this item outside the UK - shipping costs will have to be calculated before orders can be accepted.