Endorfins KS1 Fin Review

Endorfins KS1 Fin Review

At the tail end of 2021, Kelly Slater introduced Endorfins to the market. Slater is often referred to as the greatest surfer of all time. It’s safe to say he knows a thing or two about the importance of high-performance gear. Modeled after the KS1 fin template, the Endorfins are crafted to be a more eco-friendly set of fins that still perform at a high level. After testing the Endorfins in the Futures Tri Fin Set on my Channel Island Rocket Wide, read on to learn more about what stood out in terms of performance and features.

Highlights and Features

  • Versatile template
  • Recycled P.E.T. Core
  • Produced with Eco-Friendly Materials
  • Incredibly lightweight
  • Available in FCS II and Futures

Endorfins KS1

Endorfin KS1 close up the center fin.

Background and History

Endorfins was created and crafted with the knowledge and experience of 11-time World Champion Kelly Slater. He set out to create a high-level performing fin that would be more environmentally conscious. The Endorfins thruster set is made in the KS1 template that has been around for some time. Slater’s Endorfins take this legendary template and put an all-new construction to work to create a responsive and controlled fin.

Endorfin KS1 eco friendly packaging.

Materials and Construction

The Endorfins are made using a carbon twill paired with a non-woven carbon veil. This construction is engineered to create better flex patterns and predictability. In order for the fin to float on water, the Recycled P.E.T. core is 90% air. For those wondering, P.E.T. (Polyethylene terephthalate) is the chemical name for polyester. This material is 100% recyclable and is a far more sustainable option than most other plastics.

Another cool feature is that the packaging used for the Endorfins is fully recyclable and made from recycled materials.

Keep in mind that the FCS II model doesn’t click in and out like a typical FCS II fin. The Endorfins have two screws for each fin, ensuring they are locked in snugly.

Endorfin KS1 view of the Future thruster set in surfboard.


When using the KS1, you’ll quickly notice how responsive they are. The ultralight carbon construction and pivotal template allow for quick movements and snappy turns. The fins are so light that you may find yourself double-checking they are still on your board.

The KS1’s rear fin is slightly smaller than the front two, which helps with release and allows for a loose feeling when the surf is less than perfect. The greatest selling point of the KS1s is that they perform in a wide variety of conditions. This versatility can be attributed to their controlled flex characteristics making the fins lively yet predictable as the waves get more powerful.

Available in both Futures and FCS II, the Endorfins are produced in Twin + 2, thruster, and tri-quad fin sets. Available sizes range from small for the groms to medium and large for adults.

Endorfin KS1 closeup of the template.

Value and Durability

The Endorfins KS1’s are an extremely high-performing fin at a competitive price. The carbon materials and lightweight construction give the fin set a lot of value. I wouldn’t recommend testing their durability against the impact of rocks or debris, but the fins will hold up to almost everything you throw at them.

Staff Feedback

“The KS1 Endorfins are about as surf-friendly as they are eco-friendly. The familiar template holds through turns on steeper waves and allows for speed control on the face of the wave, even in the mushy stuff. Solid fin choice for most conditions. Bonus points for being so lightweight they float on water, and for their environmental contributions.”
- Chad

Final Thoughts

“Screw your fins, not your ocean,” says Slater. As surfers and ocean enthusiasts, what’s not to love about an eco-friendly product? Bottom line: the KS1 Endorfins live up to the hype with their incredibly lightweight yet world-class performance ability. Whether playing around on your summer groveler or chasing heavy storm swells, the Endorfins are versatile enough to handle it all with their balanced template. You can also find the Enforfins highlighted in our Best Thruster Fin Sets of 2023.

If you have any questions about the Endorfins, feel free to leave a comment, call us at 1-888-546-6176, or email us at support@cleanlinesurf.com. Enjoy the water!