This is a bushing that interfaces with the injection press nozzle and connects to the runner in the plate. The sprue bushing is considered the primary runner channel and will set the cycle if it is too large. It has a nozzle the radius to match the molding press injection unit. The sprue bushing that contains the first leg of the runner. The sprue bushing can cause some problems if the wrong orifice size is used. The orifice size should always be at least .015 more than nozzle orifice to ensure there would be no undercut. In addition the nozzle radius must match the sprue bushing radii. Failure to match these two surfaces can result in a nozzle leak at the press and phenomena called a beehive will form around the nozzle costing hundreds of dollars in ruined heater bands. Beginning size orifice is determined by the amount of cavities and the gate size used in the mold. A small effective radius gauge is a good investment in the technician's toolbox that properly identifies the radii. The two most common nozzle radii is.5 or .75 radii. Misalignment of the injection unit with the mold can also cause problems. In the Avaya plant a "machinist" would fix this.