FCS K2.1 Glass Flex Fins

FCS K2 1 Glass Flex FinsThe FCS K2.1 Glass Flex fins are the world beating FCS surfboard fin set designed by world champion Kelly Slater and is one of the best selling FCS fins to date.

This fin set was previously designed in FCS’ glass fiber composite but is now available in the newer Glass Flex composite construction.

How Much Will This Fin Set Cost?

The K2.1 Glass Flex fins retail for US $55.00. Below are the current prices of this fin set at a variety of online stores and surf shops.

FCS K2.1 Glass Flex Fins  
US $55.00

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Design and Feel

The FCS K2.1 fins have been designed to suit Kelly Slater’s in the pocket style of surfing.

The fin set is made up of 2 side fins and a center fin of different sizes and fin design. The side fins, which have a base of 4.33” (110mm) and a depth of 4.53”(115mm), are larger than the center fin with a total surface area of 15.23”2 (9824mm2). The side fins are also more upright than the center fin with a sweep of 32⁰.

These side fins work in tandem with the smaller, stiffer center fin.  This fin has a base of 4.28” (109mm), a depth of only 4.41” (112 mm) and a total area of 14.22”2 (9172mm2). The sweep of the center fin is also slightly less equally 31⁰.

The K2.1 fins are also from the Glass Flex line of FCS surfboard fins.  These fins are therefore made from FCS’ new fiberglass composite using their injection molding process.  This creates a fin with the identical flex and memory characteristics of laminated fiberglass fins.

This design makes the FCS K2.1 fins a very fast and smooth set of removable fins, with quick, controlled release.  These fins will allow you to pull off some very sharp, short radius turns.

Wave Conditions

Kelly Slater says he uses these fins mostly for barreling waves and beach breaks on the WCT, while turning to the K3 fins for long walled waves and down the line surfing. But this fin set can be used in almost any surf conditions and can be ridden at pretty much every type of break.

The Look

You can spot the FCS K2.1 Glass Flex Fin from a mile away as they still have the cool, original art work of the Composite K2.1 fins.  This is the two side fins being white in color with a blue dot in their center and the center fin being blue with a white dot in its center.

You will also find the signature, K fin’s logo along the outside edge of the base of these surf fins as well as a K2.1 stamp.

Surfer Specifications

The FCS K2.1 fins are specifically made for surfers in the middle weight category and would therefore be ideal for surfers weighing between 130 to 180lbs or 60 to 80 kilograms. As this is one of FCS’s more advanced fin templates it is best suited for the advanced to professional surfers.

What We Say

This is a good buy if you like to surf in the pocket and your local break is a fast wave, requiring quick directional turns.  Also by investing in the FCS K2.1 Glass Flex Fin, you will be using a product that has been designed and endorsed by nine-time world champion Kelly Slater. With such a big name behind it, it’s almost impossible to go wrong and we have yet to hear someone say they hate these fins!

Fin Specifications
Side Fin Center Fin
Material Glass Flex Glass Flex
Base 4.33"
(110.0 mm)
(109.0 mm)


(115.0 mm)
(112.0 mm)


(9824 mm2)
(9172 mm2)
Sweep 32° 31°
Foil Flat
Flex Stiff Stiff

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