You need modified 12 point box end wrenches. It made the job easy because you don't have to move the wrench too far to grip the nut. You will have to cut a notch or opening in the end to clear the tube that goes to the evaporator. Hope this makes sense. You can make finer movement on the nut.

__________________

1984 300SD 175,000 Miles
1987 GSXR 1385cc
1985 GSXR Limited Edition 750cc
2005 Suzuki Burgman 650cc