K4 Fins Review

K4 Fins closeup

K4 Fins

Over the last year Steve Thorp has progressed from knocking up a few prototype plastic wave fins in his spare time to building a worldwide distribution network and seeing the likes of Graham Ezzy riding his fins at Ho’okipa.

Having now had opportunity to try a few sets of K4 fins in different conditions, here are our first impressions…

Price: Fantastic! £45 for a set of K4 twin fins as opposed to about £120 for the G10 equivalent. Alternatively, the K4 quad fins will set you back around £65, whereas G10 would be around £180.

Weight: They are certainly lighter than G10 equivalents, and when you have four fins in your board that can add up to quite a difference. A K4 US box 17cm fin weighs around 100g.

Appearance: Initially, they look a bit budget against other brands, with a matt yellow finish and no logo. However, Steve says he’s chosen yellow for a reason: it s a colour that stands out and makes it obvious that they’re K4 fins. We can see the sense in this. It s almost becoming a brand in itself and the more you see, the more you recognise. In future Steve plans to print a logo on the fins and perhaps offer a colour option for those who really don’t like yellow!

Performance: Before we go into specifics it’s important to point out that, because we can’t compare a plastic K4 fin with exactly the same shaped G10 equivalent, it’s hard to distinguish exactly which performance factors can be attributed to construction / flexibility, and which are the result of shaping and foiling differences. So, taking both these factors into account, these are our overall impressions of how the K4 fins perform.

Straight Line: We were expecting this to be their weakest area, but we were really surprised. On our small quad-fin boards we couldn’t discern any negative difference at all when powered up (from the standard set of G10s), and there was noticeably more control at the top end, with less tendency to spin out. There was perhaps a tiny bit less drive for early planing, but it was very minimal.

With the bigger twin-fins the differences were exaggerated a little more. At the bottom end the drive wasn’t quite as good as G10 (but still perfectly fine for almost all wavesailing needs), while at the top end the control was better and again less prone to spin out.

Riding: Our first impressions on both twin fin and quad fin boards are that the K4 fins grip through the turn better with more predictability than G10, and don t break out as much in the top turn.

Delving a little deeper, in cross shore wave conditions, during the last quarter of the turn (bottom and top), it feels like the K4 fins are able to maintain more drive, enabling the board to keep powering through the turn and through higher radius arcs. In the bottom turn this allows you to get more vertical, while in the top turn you are able to feel more grip, which translates into acceleration as you whip the board around.

In cross on conditions the board feels looser underfoot, grips with more bite in the bottom turn, and also seems to transition from bottom to top turn with more control, which is particularly noticeable when overpowered. When the fins do break out they do so in a very controlled manner, allowing you to pull them back at will.


Our first impressions are that K4 fins provide very good grip with a really nice balance between drive and looseness off the top. They will make your board livelier, yet more controllable. They’re perfect for any wavesailor who’s focused on waveriding, and the pricing is as impressive as the performance.

RRP: Sizes: Colours: More info:
£45 Twins, £67.50 Quads Main fins – 12-17cm every cm.
Side fins – mini Tuttle 8 / 10 / 11 / 13cm and US box 7 / 9cm sides
Anything you like, as long as it s yellow!


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