Metal Round Joiners ModelSize (inch/mm) QSM-RJ-1004/100 QSM-RJ-1506/150 QSM-RJ-2008/200 QSM-RJ-25010/250 QSM-RJ-30012/300 QSM-RJ-35014/350 QSM-RJ-40016/400 QSM-RJ-45018/450 QSM-RJ-50020/500 Description The LinkedAir neck adapator (Square to Round) is made out of galvanised steel and used for the connection of round duct. Custom sizes are available upon request. Product Code QSM-RJ