The Fast Fender was designed in conjunction with downhill legend Steve Peat. It mounts to the bars rather than into the steerer tube, will fit any bike and is made from what can only be described as near-indestructible plastic.
The idea is to catch mud and spray as it gets fired off your front tyre. At speed, you catch up with this spray and it ends up splattering your face and goggles, affecting your vision.
It does a damn good job too. When riding with people who didn’t have them fitted, their goggles were plastered with mud by the bottom of a run, and ours weren’t.