Been suitable for 34/40/44 and 50 HP engine of 1200-1600 ccm inclusive. Mexico beetle… NOT FOR BUS ENGINES WITH 1,7-2 LITRES and 24.5 + 30 HP engine suitably…. Aluminum with feather/spring… always stops the correct tension by the feather/spring. These pipes can insert you without the cylinder head to dismantle… to please to consider you that the short end with feather/spring to the cylinder head are installed…. Quotation per piece with seals