Abstract: In a well pumping unit of the type employing a polished rod, a stuffing box is disposed at the upper end of the wellhead which has axially spaced bearing assemblies, and packing coils positioned between a bearing section at either end of each assembly to guide the polished rod for reciprocal movement along a vertical path through the wellhead, each bearing section having annular portions connected together in end-to-end relation with one portion composed of brass and another portion composed of zinc which is capable of undergoing a reduction reaction with the oxygen present in the liquids and gases to effectively reduce corrosion of the polished rod.