HD 6R12PP. 12mm threaded. Used with 18mm spark plug socket. Equipped with a U-groove platinum tip. Platinum plugs are more durable, have a wider heat range and will work with a lower voltage. By maintaining a precise gap over a longer period it will provide a longer life than regular spark plugs. Custom replacement for OEM 32362-04A (regular) and 32329-97 (platinum version).