Piston 72mm +30". Short Isetta Piston compression Height 38mm Hepolite Part No 15043 This piston is for a short barrel engine and must not be confused with the longer piston with a compression Height 48mm Hepolite Part No 14317 that is normally fitted to nearly all engines and a very very few engines have the short type you may ask why ? Well we don’t know!! Please note they are not interchangeable unless you want a very low compressionthat wont go up hills? Dimension above piston pins = 25.37mm Below pin = 21.5mm Pin Diameter (Gudgeon Pin)  = 20mm