Waterway 1" Top Access Silent Air Control [1 5 8" HS, 2 9 16" FD] [Scal] [Gray] (660 3567) americanpool A unit like this is A unit like this is useful because it provides a compact complete filter replacement for systems that use a smaller cartridge filter format where maintaining dependable structural fastening and sealing compression is essential to overall filter reliability This Waterway air control is a strong choice for compatible spa systems that need dependable airflow adjustment with a clean The Waterway 660 3567 top access silent air control is designed for compatible spa air systems that use a 1 5 8 inch hole size and a 2 9 16 inch face diameter