Futures fins slide into a single slot, while FCS II fins fit into two grooves ... but with fiberglass/honeycomb construction.” Foil refers to the shape of the side of the fin.

[L to R] Futures, FCS II, Lib Tech fin boxes. The three most common types ... but with fiberglass/honeycomb construction.” Foil refers to the shape of the side of the fin. It determines how ...