Hobie Mirage kayak users report as much as 10% increase in speed using ST TURBO Fins. But its not all about speed, you can get top end speed and a slower cadence for cruising (Less pedals per mile). All achieved with these larger and more efficient fin designs. Increase your performance or increase your fitness routine, you choose the fin that is right for you: Standard, ST or ST Turbo... low, medium or a higher gear! The standard fins, supplied with our kayaks, are the easiest pedaling fins, but many users feel that the standard fins do not offer enough resistance. This is very evident when using our sailing kits. The added power and speed of the sail often outpaces the standard fins (similar to pedaling a bike down hill in first gear). Want to go really fast? Add the ST TURBOs for sailing! The longer fins can also increase lateral resistance for sailing upwind. These ST (Square Tip) designs will require a bit more effort to pedal. The added effort is commonly compared to pedaling a bike up a slight incline. In addition, the included fin tension screw allows adjustment to achieve lower end torque or top end speed to meet the desires of the pedaler. The ST TURBO fins require longer masts. The ST TURBO fin kit comes with 2 fins, 2 masts and all needed fittings.