Scan Your Fin Box — Instant AI Match
Take a photo of your fin box and get an instant compatibility match.
What fin system is your board running?
Scan a photo of your fin for an instant match, or pick your system manually.
✔ 95% recognition accuracy · ✔ No app required · ✔ Built by surfers in Munich
Photo of your fin box
Show the fin plugs clearly — good lighting helps.
Drag & drop or click to select
JPG, PNG, WebP · Max 10 MB
Tips for best results
- Make sure the fin base / plugs are fully visible
- Shoot in daylight or bright indoor light
- Avoid strong shadows across the fin box
Analysing your fins…
Checking your setup
Which fin system do you have?
Pick the system that matches your fin box.
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Not sure which fin system your board uses? Choosing the wrong fin is the fastest way to frustration. This guide helps you identify your surf or SUP fin box in seconds — whether it’s FCS I, FCS II, Futures, US Box, Slide-In or Quick-Lock.
Identify Your Fin System in Seconds
Every surfboard and SUP board uses one of six common fin systems. Buying the wrong fin means it simply won’t fit — and returns are frustrating. Our AI-powered fin scanner identifies your system from a single photo in under 10 seconds, with 95% accuracy.
You can also use the visual guide below to identify your system manually, or compare all six systems side by side in our compatibility table.
- 📸 Scan your fin box with our AI tool
- 🔍 Use the visual comparison guide below
- 📚 Learn the difference between all major fin systems
What Fin System Do You Have?
Most modern boards use one of six common fin systems. Use the descriptions below to identify yours manually — or scroll back up to use the AI scanner for an instant match.
FCS I (Two-Tab System with Screws)
How to recognize it:
- Two small tabs at the base of the fin
- Secured with two grub screws
- Common on boards before ~2013
FCS I is the classic dual-tab system. Reliable, simple, and still widely used. The two protruding tabs slot into matching holes in the fin box, held in place by grub screws on either side of the board.
⚠️ FCS I fins do not fit FCS II boxes without adapters.
FCS II (Tool-Free Click-In System)
How to recognize it:
- Click-in mechanism — no screws required
- Clean moulded insert inside the box
- Most common system today
FCS II allows quick fin changes without tools. It’s currently the most widespread surf fin system worldwide. A simple push-and-click locks the fin in place; a squeeze of the tab releases it.
Some FCS II boxes can accept FCS I fins with screws — but not always the other way around.
Futures Fin System (Single Base Design)
How to recognize it:
- One long solid base that spans the full box length
- Secured with one screw
- Longer contact surface inside the box
Futures fins use a single-piece base for increased stability and energy transfer. The longer base-to-box contact area gives a direct, stiff feel — popular in performance shortboards and high-performance surf setups.
US Box (Longboard & SUP Standard)
How to recognize it:
- Long center box running lengthwise in the board
- Adjustable metal plate with a single screw
- Fin slides into a track for position adjustment
The US Box is the universal standard for longboards, touring SUP boards, race SUP boards and river SUP boards. It allows full adjustability — slide the fin forward for maneuverability, back for straight-line tracking.
Quick-Lock SUP System
How to recognize it:
- Tool-free click-in design
- Often found on inflatable SUP boards
- No screw plate
Quick-Lock systems allow fast setup without tools — ideal for travel and rental boards. The mechanism is similar in principle to FCS II but designed specifically for SUP use. Look for the click-tab release mechanism at the fin base.
Slide-In SUP System
How to recognize it:
- Single base design similar to Futures
- Requires one screw to secure
- Common on inflatable SUP boards
Slide-In systems resemble Futures surf fins but are designed specifically for SUP use. The fin slides into the box lengthwise and is locked with a single screw. Check your board manual if unsure — or use the scanner above.
FCS vs Futures vs US Box — What’s the Difference?
Choosing the right fin system isn’t about performance first — it’s about compatibility. A fin that doesn’t fit your box is useless, regardless of how good it is. Use the table below to quickly compare all four major systems.
| Scrollen Sie von links nach rechts | FCS I | FCS II | Futures | US Box |
|---|---|---|---|---|
| Tools Needed |
Screws
|
No tools
|
One screw
|
One screw
|
| Typical Use |
Surf
|
Surf
|
Surf
|
SUP & Longboard
|
| Most Common On |
Older shortboards
|
Modern surfboards
|
Performance boards
|
Touring & race SUP
|
How to Choose the Right SUP Fin
Once you know your system, the next step is performance. Different conditions require different fin shapes.
Best SUP Fin for Rivers
- Shorter depth — reduced bottom strike risk in shallow water
- Slight flexibility for dynamic river flow
- Designed for shallow standing waves and river currents
Best SUP Fin for Touring & Lakes
- Longer fin for better straight-line tracking
- Improved glide efficiency per stroke
- Ideal for distance paddling and calm flatwater
Best SUP Fin for Racing
- Narrow, high-aspect shape for minimum drag
- Maximum efficiency per stroke
- Built for speed and competitive performance
Compatible Fins for Your Board
Made in Germany from bio-based materials. Engineered for performance and sustainability.
Common Fin Buying Mistakes
Avoid these typical compatibility problems:
- Buying the wrong fin system — always check your box before ordering
- Choosing too long a fin for shallow rivers — bottom strikes will damage your fin and your board
- Ignoring screw compatibility — FCS I and FCS II use different hardware
- Not adjusting fin position in US Box systems — forward for turns, back for tracking
If you’re unsure — scan your fin box above and get a precise match in seconds.
Tested by Competitive Athletes
Our fin designs are developed with input from competitive river surfers, touring paddlers, and members of the German Rowing Federation during prototype testing.
Every fin balances stability, glide, control, and sustainability. Made with bio-based materials and engineered in Germany — built to perform and built to last.
Frequently Asked Questions
-
FCS II is currently the most common surf fin system worldwide. US Box is the most common SUP fin system, used on touring, race, and river SUP boards.
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Some FCS II boxes accept FCS I fins with screws. The reverse is not possible without adapters. When in doubt, check your board's spec sheet or use our fin scanner above.
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No. SUP boards typically use US Box, Quick-Lock, or Slide-In systems depending on the brand and board type. Always confirm compatibility before purchasing.
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Only on longboards that have a center US Box. Shortboards use FCS or Futures systems. US Box fins will not fit FCS or Futures boxes.
-
Check the length and mounting mechanism of the box in your board. When in doubt, use our AI fin recognition tool above — one photo is all it takes.