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About K4 Fins

About K4 Fins

K4 Fins specialise in innovative & revolutionary performance wave, freestyle, freeride & freestyle-wave windsurfing fins. Our fins are unique to windsurfing. They’re made using plastic composite – giving them extra flex, reflex & outstanding performance.

Our dedication to water time and designing the best performing products on the market means that we are constantly innovating and expanding our product range so that we can break new ground.


How we started


Living at the furthest point inland from the sea, but as he points out “with the best access to any windsurf or surf spot in the UK and surrounded by airports”, British pro windsurfer Steve Thorp started his brand of windsurfing fins, K4 named after his sail number.

Nearly 30 years of watching for a forecast and driving vans around the country to take advantage of the best windsurf conditions didn’t always pay off and Steve used these opportunities to score epic surf. The surfing showed Steve missed opportunities in windsurfing. He was able to get far greater maneuverability, speed and looseness from surf fins than those used in windsurfing. The evolution of mulitfins fins added to this opportunity but Steve saw how he could use his scientific and engineering skills to get what he wanted for windsurfing.


”I always wanted to study boat design but was persuaded by careers advice to do a Civil Engineering degree which at least had some fluid dynamics involved. Now I work in injection moulding and toolmaking so I’ve managed to combine all of these skills and become a windsurf fin designer and manufacturer. Pretty lucky really!”


Performance windsurfing fins


After years of testing and development, K4 Fins are now stocked worldwide and we have a range that covers not only windsurfing but SUP, kite and shortly surf fins to suit all riders and styles.

Our speed windsurfing fins have done over 50 knots on the speed course and are used by many of the world’s top watersports professionals. The wave fins have ridden the infamous big wave surf spot Jaws and the offshore slab at Pedra Branca in Tasmania.

We have the help and support of our riders and the Official Test Centre in Weymouth to thank for our continued progression and we’re really excited to have you on the yellow fins!



Our materials


Our materials offer unique performance that you won’t find in any other windsurf brand.Our materials are unique to the windsurf market. From the original Dynamic Flex material which was designed to deliver better wavesailing performance, to our latest 2016 Super Stiff material we have spent years designing, testing and modifying our material and mould processes to get a material that provides the perfect flex patterns for windsurfing.

We looked for the qualities that would match up with the performance that was needed to deliver the results in windsurfing we sought.


Dynamic Flex

K4’s classic Dynamic Flex material with the black logo gives flex that works with the power you’re putting in allowing you to drive hard and fast and giving power back for turns. Its ability to flex and spring back to its original shape means crazy grip at extreme angles of attack and epic round house turns. The flex makes it easier to crank back up hard at the critical section, then gouge or power through the lip at full velocity

“The flex allows me to go more vertical and hit later lips. Instead of getting stuck in the curl, I can push on top of it and get more projection. Super cool.” Graham Ezzy

These fins are lighter, snappier and are extremely robust.

Super Stiff

Available for 2016’s Leon, 3SW, Fang and selected front fins , we have developed an alternative to our original flex material that compares with the stiffness of a G10 but with faster reflex and better memory for speed, maneuverability and acceleration making this material the perfect fit for the all-rounder Leon, 3SW’s waves, freestyle or bump and jump capabilities or for freeride windsurfing with the Fang fin.



K4 Fins are able to offer you the best fin prices on the market, yet high end performance due to our agile business model. We’re not a big company and we make all our products in house in the UK which means that the process is streamlined without incurring additional costs.

This benefit is doubled to you because you get a saving on the product cost as well as high performance meaning that you can get as many fins as you need to meet your needs.


Made exclusively in the UK


By buying K4 Fins you are supporting a UK business but you get to benefit from the unique expertise that we have in both engineering and windsurfing. We do everything in house because we care about our product design and quality. We’re able to work without shipping times and language barriers from overseas meaning that our product doesn’t become diluted. If we find a modification or a tweak that we think will help your performance we’re in a position to pass that on to you instantly meaning that your feedback directly improves your product.

We CNC and mould all our fins using precision moulding techniques and we have designed and developed the latest fin ranges in conjunction with the Official Test Centre (OTC) in Weymouth.

Not only do you get British quality, but as we don’t import from China or other countries we are in control of all our manufacture and you know that you’re buying from a company that’s adhering to British standards of employment, health and safety and British employment law.