Piston pump plug.
Services 1953 thru 1964 four cylinder gas or diesel tractors with piston type pump. Tractors: NAA, 501, 600, 601, 700, 701, 800, 801, 900, 901, 2000, 4000. Will service either NCA600C or NCA 600F pump.
Also fits 1965-1975 Ford 2000, 3000, 4000 series tractors with 3-cylinder gas or diesel engines.