Rotating flat surface mount. It's actually slightly concave on the bottom to curve against a helmet. Lets you adjust the up/down. ONLY thing is you need to find a happy place for the mount in the front/back position on the helmet, otherwise the camera will be aiming sorta sideways. Depending on your helmet, there's a fine line between mounting it low enough to get a good spot without interfering with goggle straps. Then you need to mount it far enough forward to avoid having your helmet in all of your vids, without having the camera looking across the front rather than forward (like Desired mentioned). Then adjust the up/down, and the finally adjust the turn knob on the front of the lens to make sure it's recording perfect level.
Sounds complicated, maybe I'm fussy, but the beauty is that it is all adjustable. I don't want the camera on top of my head, I want it near the side, so I had to fuss around with the forward/back, up/down, and lens rotation to get it exactly where I wanted. But once it's dialed in then it's just click and go from then on out.
You just need to find the sweet spot for your helmet setup.