HKS D1 Limited edition radiator cap Brand HKS (Japan) Website HKS-Power.co.jp Part number 15009-AK004 Like most aftermarket options, my Golpher radiator uses an S-type radiator cap. For the stock ST185 radiator you'd need an N-type cap (HKS part number 15009-AK003). Related links Golpher high capacity aluminium radiator Modifications - Engine Top