Protect the pipeline: Pool Pillow can block the water return pipe to prevent rainwater from entering and freezing, which helps prevent the pipeline from breaking and protects the swimming pool from damage. With rubber ring: Ensures sealing performance. A set of 5 winter plugs meets various needs and is suitable for use with massage bathtubs, swimming pools, and SPA systems. Easy to install and use: Simply place over the pipe return port; no additional fasteners required. Installation takes only a few minutes. High-quality material: Pool winter expansion plugs are made of durable plastic, meet standard specifications, and are designed to expand for a secure, leak-proof seal. Wide range of applications: Suitable for residential garden pools, swimming pools, and similar applications. Skimmer plug can be used to seal oil skimmers, return pipes, and detergent lines.