Use with plastic breather valves only. Large hole. Note: Steel breathers require steel breather valve spacers. Plastic breathers require plastic spacers. Do not intermix steel and plastic parts. Note: The OEM plastic breather is low cost but an inferior; poor quality product that will cause damage to crankcases in the breather bore since it is prone to distorting. The sooner this stock type breather is removed; the better. We highly recommended to replace it with a steel breather valve; like was used in earlier engines.