Probox fin boxes are designed to accept different inserts that change the cant of the fin (the angle in relation to the bottom of the board and the side of the fin) so that you can tune in your ride. Inserts are available in 0, 4, 6, and 8 degree as well as solid inserts to plug boxes not being used.
HDM Eliptical Keel SUP Fin featuring tooless Click-It install system.
HDM fins are a high density molded fin that features a special blend of fiber and mix of plastics to yield a lightweight but stiff fin at an economical price. HDM fins will be approx. 25% lighter than solid fiberglass fins.
Simply slide the front of the fin into the box channel and then press the base down into the box. Spring loaded ball bearings click into the channel and hold the fin in place.