Before you buy fins, you need to know what boxes are in your board. There are three main systems and they are not interchangeable.
US Box
A single long slot, usually in the centre of a longboard or mid-length. The fin slides in and is secured with a bolt and screw (sometimes called a plate and screw). You can adjust the fin position forward or back in the box to change how the board turns.
Our longboard fins all use US Box and come with hardware.
Futures
A single-tab system. The fin has one flat tab that slides into a pocket in the board and locks in place. No screws, no tools. Clean, solid connection.
Our twin fins and keel fins come in Futures-compatible bases.
FCS I
A dual-plug system. Two small tabs sit in two plugs in the board, secured with grub screws (usually included with the board, not the fins). Older system but still widely used.
Our FCS I twin fins use this base.
What about FCS II?
FCS II is a newer keyless system. Our FCS I fins will not fit FCS II boxes without an adaptor. If your board has FCS II boxes, check if the manufacturer included compatibility plugs.
How to check your board
Flip your board over. Count the fin boxes and look at the shape of the slots. One long slot in the centre = US Box. Single flat-bottomed slots = Futures. Two small round plugs per fin = FCS I. Two small slots with no screw holes = FCS II.
Still not sure? Send us a photo at hello@finblanks.com and we will tell you.