HYDRO FLASK Wide Mouth Flex Straw Cap. Hydration on the go just got easier with our leak proof, insulated Flex Straw Cap. Add it to your favorite Wide Mouth bottle easily enjoy cold hydration anywhere. Fits all Wide Mouth Hydro Flask bottles. Imported.Products Benefits:- Straw cap makes cold refreshment that much easier- Flex strap- Leak proof Cap- Honeycomb Insulation- Dishwasher Safe BPA – Free- 2 straws included.