These pool cover water bags are designed to add reliable weight and stability to an inground pool cover during winter closing. The double-chamber design helps reduce rolling and shifting in strong winds, while durable 0.4 mm PVC construction resists UV exposure and minor impacts. Leak-resistant welded seams and twist caps with rubber gaskets help provide a secure seal during seasonal use. The 6-piece set is easy to fill, drain, and store for recurring winter pool maintenance.