S3 GAS GAS PRO CYLINDER HEAD AND INSERTSThis cover is the latest S3 Head for GAS GAS TXT 250 280 300 with the horizontal water hose outlet. The various inserts for this head are also available to buy separately. If you want fairly flat power for beginners or for really slippery conditions then you would set the bike up with a low compression insert. If you want to keep the bike standard, order the standard insert. If you wanted a more aggressive power setup, or you are going high in