Expansion coupling ideal to use in long runs of conduit to allow for thermal expansion. PVC is to external corrosion and pitting and will not rust. Offers high impact and high tensile strength. As a building material PVC offers outstanding fire performance characteristics. Retains original properties after years of exposure to direct sunlight, heat, and extreme weather. to a wide range of chemicals such as acids, alkalis or salt solutions. to fungi, action, rodents and termites, for a long and trouble-free life. Check local codes for the correct number and spacing required. UL (Underwriter's Laboratories) listed.