FCS thruster and quad fin’s come with fin rating’s. These fin rating’s provide the drive, pivot and hold characteristics of each individual fin set based on the element’s such as area, base length, sweep, depth material and template. FCS provide’s fin rating’s as a guide to individual performance. They can also be used as a reference when choosing a fin for specific performance requirements. If un-sure about the fins for you, you can go to the FCS web site and use the fin selector program or come in and use the FCS test drive fins in store.