Never officially sold to the public, but a handful were purchased from Geissele. The $5k GunBroker listing above is from a few years ago when there weren't any of these triggers in private hands. Now you can grab them from collectors who have them for about $2,000 or a little less. There's probably 2 or 3 dozen of the real Mk13 Geissele triggers currently in private collections, so they're still pretty rare.