This little piece will allow you to mount your bottle cage onto your handlebars, for super fast re-hydrating!
They are made of extruded aluminum and are intended for city bikes. So they fit bars up to 25.4mm.
(I know some of will want to use them on the 26mm "sleeved" road bars. In that case you'll need to file just a touch off the top edge of the "hinge" section so it opens a little wider. Of course, it's no problem to use them on "bulged" road bars.)