This is the Barfly GoPro Bottle Top Mount for Specialized/Purist or CamelBak water bottles. So if you just can't decide where your GoPro or similar compatible camera should mount, it clearly goes on top of your bottle. Duh. The angles you can shoot from inside of the frame allow for some pretty compelling video and it doubles as a quick access selfie stick. It is a super stable location and for racing and crits so you can capture some amazing action shots. Plus people can see your larger than life guns. Everybody wins.