Pool Pads help provide a protective barrier between your new liner and the ground. This can help add years to the life of your liner. These pool pads are made from a special high-density polyethylene foam. This pad lays easily under your liner and helps to protect against sometimes abrasive sand under your pool. The Pool Pad is 1/4 of an inch thick. Fits pools up to 18' Rd., 15'x25' Oval and 16'x24' Rect.