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The fin guide

Know your fin and you know your surfinlock! 

FCS 1 fins

FCS 1 fins are widely used and to be found in shortboards, funboards, mini malibus, and sometimes as side fins in surf longboards or paddleboards. You can easily recognize an FCS I fin by the 2 tabs on the underside, which are made for the fin plugs. An FCS 1 fin is fixed in the board with 2 side grub screws.

Fin plugs for FCS 1 fins

FCS 1 fin plugs can be different in shape but have always one thing in common: they have 2 grub/fin screws on the side for fixing the fin. FCS 1 fins can also be used in FCS 2 plugs since they also have holes for side grub screws.

Use the new surfinlock FCS or our original surfinlock FCS design for boards with FCS 1 fins.

FCS 2 fins

FCS II fins feature two tabs, one of which is longer and has a groove. This unique design allows the fin to be clicked into the fin box without the need for screws, but we recommend using the additional screws for added security. Accidentally hitting the reef or sand can cause the fin to become loose and potentially lost. FCS II fins require FCS II plugs.

FCS 2 fin plugs

FCS 2 fin plugs feature a unique "8" shape outline with two integrated slots and two threaded holes for grub screws. These plugs are compatible with both FCS 1 and FCS 2 fins, making it easy to switch between fin systems. FCS 2 fins can be clicked in the fin plug without any screwing but we recommend additionally fixing them with the fin screws. Note that not all FCS 2 plugs come with grub screws, so be sure to check and purchase them separately if needed.

Use the new surfinlock FCS or our original surfinlock FCS design for boards with FCS 2 fins. We also have fin screws in our shop.

Futures fins

Futures fins stand out with their single tab extending along the entire base. This tab features two grooves, one larger for hooking the fin into the fin box from one side and one for the front-facing grub screw that secures it in place.

Futures fin plug / fin box

The Futures fin plug, also known as the Futures fin box, is designed with a single grub screw that secures the fin from the front, providing a secure and reliable fit for your surfboard.

Use the new surfinlock Futures for all boards with Futures fins.

US Box fins

US Box fins are easily recognizable by their unique design, featuring a pin and a top screw that enters through the fin in a small metal plate. These fins are commonly used for longboards, other single-fin boards, many SUPs, and some windsurf boards. To secure US Box fins, they must be screwed from the top.

The US Box

The US Box fin system features a long slot that can vary in length depending on the type of board. It's commonly found on single-fin boards, as well as many SUPs and some windsurf boards. On inflatable paddleboards, the US fin box often protrudes. To secure a US Box fin, simply screw it in from the top using a small metal plate and top screw.

2 parallel US Boxes for foil boards

Foils are attached most commonly with 2 parallel US Box slots. That means you can also secure them with our surfinlock US Box.

Use the surfinlock US Box to secure your single-fin longboard, your paddleboard, your windsurf or foil board with US Box.

Slide-In fins 

Slide-in fins are a popular choice for many inflatable stand-up paddleboards. They're extremely easy to install without requiring any tools - simply slide the fin into the fin box and secure it with the plastic peg that comes with it. You can easily recognize Slide-In fins by their flat base and the plastic peg used to secure them.

Slide-In fin box 

Slide-In fin boxes are commonly used in inflatable paddleboards and stick out a little bit from the board. This type of fin box has one open end, which allows you to easily slide the fin in and out.

Use the surfinlock SUP Slide-In as a paddleboard lock for your inflatable SUP.