This performance center fin is based on a deeper thruster back fin moved forward with side fins smaller than a full thruster setup and is perfectly matched to my 4.25 side fins. This combination is a smooth, stable, good all-around design that can hold some serious rail in solid conditions. This setup works very well with a combination of tail width, rocker, rail shape, and bottom contours. They are ideal for mid-lengths as well as hipro longboards.