(10mm Gudgeon pin) The MHR Replica is a 70cc aluminium racing cylinder comparable in performance to Polini Corsa. As the MHR Replica is made of aluminium, which dissipates heat better than cast-iron, it has much better thermal properties than the Corsa though. In order to ensure sufficient inner cooling and to achieve good performance, we recommend at least a 17.5mm carb. We also suggest using a Stage6 Pro exhaust or the Nardo from Top Performances. Yasuni C16 offers high revs, but top performance isn't that good.