These are made from 1mm thick real Carbon Fiber. They mount on the inside edge of the front sponson of tunnels and help provide straight line stability at speeds. Comes with 3M VHB double sided tape installed already. These can easily be trimmed to fit your application with a belt sander (take care from dust) or saw/Dremel. They come in three different sizes (small, medium and large). The small size is suited for .21/3.5cc size hulls, the medium is suited for 7.5/11cc sized hulls, and the large is suited for Gas hulls. These come in a set of two (2) fins.