Old hs33. according to some German forum the old ones have smaller diameter pistons which equals in more braking force.
Don't quote me on that but they sure do brake very well.
I had to exchange the Evo 1 studs to the Evo 2 attachment to make more clearance for the tires though. So it's old HS33 brake levers and calipers together with the new magura evo2 attachment.
The rear brake really makes a difference compared to the cable actuated one before. it was really mushy due to the long housing and cabling. now it's really crisp and controlled.