Hydrapak Polar Surge Insulated Ascent BottleFeatures Surge valve technology maximizes flow rate and self seals to eliminate leaks and splatter during activity. Tri layer Insulation combines an external reflective heat shield with a layers of insulating foam to keep liquids cool. Flexible, ultra light materials and the unique grip groove combine for a sure hold and high flow squeeze. Made with bicyclists in mind, the Polar Surge bottle fits a variety of Bike frame sizes and bottle cages.