These 99831521-R2 S-Series Replacement Tracks are for our Dolphin robotic pool cleaners. Designed for 21st-century pool owners, our smartest, most advanced robotic pool cleaners is here to deliver a whole new level of pool cleaning performance. Each Dolphin model is masterfully crafted to provide incomparable pool scrubbing and cleaning, with a cutting-edge water filtration system, and the best warranty on the market.