GoPro HERO Camera Helmet Front and Side Mount

The standard flat or curved bases are part of this kit. The mount is attached to one of those bases either on the side or, in the case of Mountain Bike open face helmets, to the top. The mount then supports the standard attachment to the camera. There is a round pivot that allows the camera to be pointed where you want without being hampered by exact pivots that only go in one direction.
If you are looking for something for a motocross type full face helmet that attaches around the mouth area, there are other kits that attach differently. This kit can be used with an extension or two, attached to the side, but still place the camera in front of the lower area of the facemask.
You can see mounted examples on the GoPro web site
HTH,
Craig