the coldest water standard size mouth hydro sports straw cap flip top lid - multi-compatible with standard flask mouth size stainless steel water bottles the coldest water the coldest water insulated cap, patent pending, was initially built for professional athletes in high-performing sports. we believe in taking cold water on the go wherever you are, whether you are biking, cycling, running, jogging, or going to the beach. this cap allows you to drink effortlessly with one hand. simply flip the top, and drink water from it. it is easy to clean. the flip-top has a unique tab that allows you to push it without your fingers touching the mouthpiece. multi-compatibility technology: we believe in multi-compatibility, so we've extensively tested this with the coldest water bottle, as well as other stainless steel bottle brands.