If the motorhome's air brake relay valve or air booster can does not have an open port, use either a ½" tee (part number 450076) or a 3/8" tee (part number 450077) to attach the BrakeMaster air line.
For BrakeMaster 9100 and 9160 systems.

450076 ½" Air Line Tee
450077 3/8" Air Line Tee