If you have swapped your heat exchangers for J tubes then you are going to need a pair of these tinware extensions. As J tubes dont have the outer casing (as found on heat exchangers) the original lower tin no longer extends out to the exhaust, this missing tin allows critical cooling air to spill out running the risk of overheating.
These extension pieces simply fit to your lower tin and block the gap allowing the cooling air to circulate over the engine as intended on Air-cooled Type 1 engines from 1960 on.
