FiNS they can Tune your Board into a Fine Instrument or leave it wanting to break free...and Run ! This is me on a Handshaped 6'3'' for Ulu back in 2008. It was to Loose but some things felt really good about it. Never liked Loose Boards always like some resistance to Push and Power Against. FCS had come out with Full Carbon Fins and I tried a set off Advice from a Friend. Hated them ! To Stiff ! LOL I was used to the Stiff Flex of Fiberglass Fins Custom Made by Master Brian Bills in Hawaii... But it clicked = " Board to Loose ? Try the Carbons!" Bang a Magic Board emerged from confinement ! Best part of a Fin System is Tuning. And a Bonus about Custom Surfboards is The Shaper is there to suggest Fins for your Height, Weight and the Design you are Ordering. You won't get that Experience and Knowledge Buying off the Rack!