Hydro Flask Standard Mouth Flex Cap is a replacement bottle cap for all Hydro Flask Standard Mouth bottles.Strong yet flexible, our Standard Mouth Flex Cap is the perfect companion for spontaneous campouts, epic road trips, and everything in between. Made with stainless steel pivots and an easy-to-carry strap, this cap has Honeycomb Insulation to help keep your drinks cold for up to 24 hours or hot up to 12. Compatible with all Standard Mouth bottles Honeycomb Insulation helps keep cold drinks cold and hot drinks hot Durable, stainless steel pivots allow the strap to move easily BPA-Free and Phthalate-Free Fits (click below links): Hydro Flask Standard Mouth Insulated Bottle (18oz) Hydro Flask Standard Mouth Insulated Bottle (21oz) Hydro Flask Standard Mouth Insulated Bottle w Sport Cap (21oz) Hydro Flask Standard Mouth Insulated Bottle (24oz)