This is the fin sistem of my board and many Brazilian boards these days...
It uses a slot and a small scew, witch is a very obvious way to deal with the whole ting, but the cool abou it is that you can change the position of your back fin, more to the back for stability and more to the front for faster maneuverability, and you can change the angle of the lateral fins for more or less turning
anyone heard about this fins or something similar to it?
it is quite nice..