DMT has been making diamond sharpening stones in Marlborough, Massachusetts since 1976, and they're the company that put diamond plates on the woodworking map. Industrial diamonds bonded to a flat steel base means a stone that cuts fast, never dishes, and handles hard Japanese steels and modern alloys without complaint. No soaking, no flattening, no fuss.
Coarse to extra-fine grits for chisels and plane irons, the Dia-Flat for keeping your waterstones true, and the Diamond Wave for getting an edge on curved gouges and the inside of carving tools. American-made and built to outlast just about any other sharpening kit on the bench.