Abstract: An apparatus for injecting plastic material comprises a manifold having a melt channel and a flat sealing surface, and a nozzle assembly seated directly against the flat sealing surface. The nozzle assembly includes a nozzle body having an axial channel aligned, in use, with the melt channel in the manifold for communicating a flow of material therein. The nozzle body has a non-flat sealing surface adjacent the flat sealing surface, thereby forming a sealing interface to seal the nozzle body with the manifold. The flat sealing surface may be on an end of a bushing mounted into the manifold. The non-flat surface may have a conical profile, preferably defined by an angle less than one degree, and preferably between 0.2 to 0.4 degrees, from a plane parallel to the flat sealing surface. The non-flat surface may have a spherical profile, preferably having a radius between 350 mm and 4000 mm.