Abstract: A generally cylindrical restrictor insert for containing an axially movable, apertured restrictive member, housed in a flow control distributor housing of an orifice expansion device used for bi-directionally-flowing pressurized fluid, with a housing passageway being closed off via an annular adaptor flange also having an internal filter, the restrictor insert having a central axial through bore with a plurality of adjoining bore portions defining a central bore cavity, the restrictor insert also having a leading portion, with a frusto-conical front end surface, and intermediate and trailing portions, the latter having a shoulder portion and an annular end face, the restrictive member being located and axially freely movable within a distributor housing central bore cavity, with the restrictor insert, in turn being located, via slip-fit insertion, in a distributor housing central passageway.