GasGas Head Insert GP-2017 Insert 300cc S3 for Original Head CoverSpecific design of the compression inlets, gives options to adapt engine setting to YOUR CHOICE, you will feel real difference between different compression options. It uses the best alloys available, to obtain a better output & more traction. The advantage of these heads is that they can hold more water and have thicker walls which helps with the cooling rate, thus improving slightly low revs power. STAR HEAD Inserts: Forged in the best aluminum