The oil temperature sensor includes the sender, metric adapter plug and sealing gasket. It installs without modification into the oil pressure relief plug opening found on most air-cooled 1960's flat-four air-cooled engines.It is not for installation in the oil-drain plug opening! Most engine experts agree the oil pressure relief plug opening in the engine block (behind the rear cylinder on the drivers side (on US vehicles with left-hand drive) is a better choice for oil temperature sensor location than installing in the dip-stick tube or in the oil pan drain opening.