The Filter Saver skimmer sock fits most skimmer baskets like a glove Elastic band holds the skimmer sock on the basket to catch small debris and prevent it from clogging your pump or filter. Catches hair, pine needles, pollen, and other unwanted fine debris. Protects the pump impeller and shaft seal from clogging and damage. Each skimmer sock is made of nylon and can be used for months.