Hayes Disc Brake Adapter Front IS QR
Hayes calipers use 74mm spacing for mounting purposes. If you have a quick release fork that has IS tabs (A.K.A. 51mm tabs) and you want to use a Hayes caliper, this is the mounting bracket you would need. It is available in 3 sizes that correspond to the size of the rotor being used.
What more can you say? It lines everything up, and is still doing it. If you're looking at buying this, then you probably know what you're looking at, and you probably need it, and it'll do its job.
Good quality and fit perfectly.