S3 Stars Cylinder Head, Outer part only.

This Outer is the older type S3 Head with the vertical water hose outlet for GG TXT 250/280/300 models up to 2014 Part number S3-GG-CO

If you need an insert make sure you ask for the old type to suit vertical head outer. Part number ST-GG-IN

The various inserts are available separately on this website.
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 altitude then you could experiment with a “high” or “very high” compression insert.