PLEASE MEASURE THE SIZE BEFORE PURCHASE: Our pool cover has 12/15/18/24/10x7/18x9ft sizes, and an additional 12-inch fabric width is added to the outer edge of the pool. Please measure the actual diameter of the pool cover before purchase to avoid incorrect size and improper use. AUTOMATIC DRAINAGE SYSTEM: Our above ground pool cover includes an automatic drainage system, which can automatically drain water when the pool cover accumulates water, solving the problem of too much water on the pool cover after heavy rain and difficult to clean. There is no need to disassemble and install it again. We have corresponding solutions for all brands of swimming pools. Please read the instructions carefully for details.