qwerty is correct, you need those two spacer/o-ring sets in the correct order, and holding them in place is a pain in the butt.
or you have to find some N.O.S. harrison compressor... not likely.
they don't make the flat face any longer. the colored spacers make it flush, and they do work.
compressor works is the best R4 new one to buy.
the sanden kit that's for sale is a better alternative though.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!