Alt Fin x Sieve Co Twin Fins: Recycled Carbon & Recycled Plastic Keels Compared
What are Alt Fin x Sieve Co Twin Fins?
Alt Fin & Co. teamed up with Sieve, a German fin maker, to build a twin-fin keel set out of recycled material instead of virgin fiberglass or carbon. The collab comes in two versions: a Recycled Carbon model and a Recycled Plastic model — same shape, same performance target, different waste stream turned into fin.
Both are keel-style twins built for fish and fast, driving rail-to-rail surfing: more drive off the bottom, more speed down the line, longer arcs through turns, less pivot than a standard twin.
Alt Fin x Sieve Fins | Twin Fin | Recycled Carbon — $89
• Made from recycled carbon fiber
• Performance flex pattern — stiffer than Sieve's intermediate model, 1.4mm thicker
• Carbon content adds strength and drive while keeping the fin light
• Futures compatible
• Base: 138mm (5.4") · Height: 139mm (5.5") · Cant: 7° · Rake: 36.3°
Alt Fin x Sieve Fins | Twin Fins | Sustainable — $79
• Made from recycled plastic bottle lids — collected, cleaned, and processed in Germany — plus glass fiber
• Same stiffer, 1.4mm-thicker flex pattern as the carbon version, with a higher glass-fiber content
• Set of 2 fins · Futures compatible
• Same dimensions as the carbon version: 138mm base · 139mm height · 7° cant · 36.3° rake
Which one should you pick?
The carbon version is lighter and slightly stiffer for drive-focused, high-performance riding. The recycled plastic version rides nearly identically but leans harder into the sustainability story — literally made from ocean-adjacent plastic waste. Same shape, same twin-fin feel, different material story depending on what matters more to you.
FAQ
Are Alt Fin x Sieve Co fins actually made from recycled material?
Yes — the Recycled Carbon model is built from reclaimed carbon fiber, and the Recycled Plastic model is made from recycled plastic bottle lids processed in Germany, reinforced with glass fiber.
What boards are these twin fins for?
Fish, retro twins, and fast-rail performance shortboards — anything you want speed, drive, and long, drawn-out turns from rather than tight pivots.
Are they compatible with FCS or Futures?
Both the Recycled Carbon and Recycled Plastic versions are Futures-compatible.
