Swimline 24' Round Swimming Pool Cover + 3 4'x4' Air Pillows + Winterizing Kit Pillow Size: 4'x4' Pillows are used to push your pool cover up off the water's surface so the water won't freeze to your pool cover Pillows are used to keep water off the top of your pool cover Pool Size: Fits 24' Round Pools U.V. Inhibitors Protect the Cover From Sun Damage