Hydration on the go just got easier with our leakproof, insulated Flex Straw Cap. Add it to your favorite Standard Mouth Hydro Flask bottle to easily enjoy cold hydration anywhere. Standard Mouth Flex Straw Cap fits all Hydro Flask Standard Mouth Bottles Straw is easy to trim to fit your favorite Hydro Flask Flex Strap is easy to transport and comfortable to carry Honeycomb™ Insulated cap for maximum temperature retention Leakproof when closed so you can reliably sip and transport your refreshment without worry BPA-Free & Toxin-Free Removable components for easy cleaning. Also compatible with Small Flex Strap Packs