Abstract: A press fitted coupling device for fluid flow systems having fluid flow conduits with luer type connectors thereon such as those systems as are used in medical and surgical applications acts to convert a luer type male connector to a male luer lock fitting by means of an internally threaded annular collar having an annular locking member preferably disc shaped snap fitted therewithin. The inner periphery of the locking member is sized and dimensioned to slip over the male luer type connector on one of the fluid flow conduits and to engage an anchor thereon adjacent the root section of the male luer type connector so as to hold the coupling device in assembled position.