This Copper Nozzle Holder is the piece that the nozzle threads into. The Set Screw (M106S0) on top is not included. It is held inside the Aluminum Body (M103A0) and it's shape is compatible with the ceramic isolator (M107C1). This piece has a shape that should not be confused with the Copper Nozzle Holder (M105U0) that is used with teflon isolators.
Mazak® Part # 46773300720 / 46773300721