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 prior to 2015, are the easiest pedaling fins, but some users feel that the standard fins do not offer enough resistance. ST became standard equipment in 2015 models. This is very evident when using a sailing kit. The added power and speed of the sail often outpaces the standard or even ST fins (similar to pedaling a bike down hill in first gear). Want to go really fast? Add ST TURBOs. Hobie Mirage kayak users report as much as 10% increase in speed and more 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. These longer fins can also increase lateral resistance for sailing upwind. The 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.