Give your Hydro Flask Cap a personal touch with our Flex Strap Pack. Includes three reversible Flex Straps to mix and match and Customizer Tool... Northwest color palette. Pack of three straps to change up your Hydro Flask cap. Medium size fits Wide Mouth Flex Caps, not compatible with Wide Mouth Flex Sip Lid or Wide Mouth Flex Straw Cap. Flex Strap Customizer Tool features a notch, lever and cord for easy removal and attachment of Flex Straps. BPA-Free and Toxin-Free. Flex Straps are dishwasher safe. Hydro Flask Flex Strap Pack And Customizer.