They are made by Dansk/JP Groups. I have them on my "Project Heavy Metal":
Dimensionally and from a piston size standpoint they are the same as SC calipers, and conveniently use a standard SC/Carrera pad thickness rather than a much harder to find thicker "S" pad.
With these there is no need to upgrade the master cylinder since the piston sizes are the same as every 911 since 1969 (I think).