Straw Lid for Hydro Standard Mouth Flask, Simple Modern Ascent and Other Standard Mouth Water Bottle. New Improved Design, Double Wall Insulated Lid for 1.91" Mouth Size. Fit Most 12 oz, 18 oz, 21 oz, 24 oz Bottles. Double Wall Insulation Design Inspired by Nature. Help Keep Drinks Cold for 24 Hours, and Keep Hot for 12 Hours. New and Improved Silicone Connector Design, Premium Silicone Gasket, Leak-Proof, Easy to Clean and Install. Large Straw and Mouth Piece Provide Better Flow of Drinks, Slightly Tilted Mouth Piece Increase the Ease of Drinking.