21' X 41' Oval Above Ground Swimming Pool Sun Dome. This fits 21' X 41' Oval Above Ground Pools with 26 Top Rails, Uprights, Panels. This Dome comes with 1 door and 3 windows. Warming and heating is one of the key benefits - it warms the air(40 degrees) and water with solar heat up to 20 degrees Fahrenheit. It also protects your pool from leaves, bugs, debris and early spring or late summer breezes. Moreover, because your pool is protected, you cut down on the use of chemicals and expensive cleaning costs.