The Polar Session 15 oz Muck water bottles are compact, allowing them to fit in places where a full size bottle won&';t. The Muckguard covers the Surge valve protecting from dirt and is easy to open. Ultralight construction make it easy to squeeze Surge valve maximizes flow rate and self-seals to eliminate spills and splatter Valve pushes closed for leakproof transport Bottle Type: Bike Material: Plastic Insulated: No Volume: 15 oz