Accessories. Fits all standard mouth hydro flask bottles. Leak-proof. Not for hot liquids or carbonated beverages. 2 straws included. Please use the instructions on back of packaging to cut the straws to the desired length. Fits 18 oz, 21 oz and 24 oz standard mouth bottles. Assembly / cleaning instructions inside. Hydration on the go just got easier with our leak proof, insulated flex straw cap. Add it to your favorite standard mouth bottle to easily enjoy cold hydration anywhere. Fits all Standard mouth hydro flask bottles. Flip and sip: Straw cap makes cold refreshment that much easier. Leak proof cap: Reliably sip and transport your drink without worry. Flex strap: Easy to transport; comfortable to carry. Honeycomb Insulation: Insulated cap for maximum temperature retention. More premium perks. Dishwasher safe. 1 reference guide for trimming straw.