12mm A/C Compression Block Off (1) S.U.R.&R's Compression Block Offs effectively eliminate failed rear A/C components and avoid the high cost of repairing these systems. .The best part is you will still be able to use your front A/C system to stay cool..Available individually or as part of the AC90M Metric Compression Block Off Kit..On the car A/C line repairs made simple.Make connections easily by hand; no specialty tools required..Compression unions and adapters specifically designed for A/C line repair application pressures rated up to 600 PSI.Drastically cuts labor time AC12MCB