Keep your Airmax Aeration System running at its best with an Airmax Aeration Maintenance Kit, Over time, seals and moving parts wear and break down causing decreased system performance, Airmax Aeration Maintenance Kits contain the parts you need to restore your Airmax Aeration System to its maximum potential, Maintenance Kits should typically be installed every 3 to 5 years, Head O-Ring [AP109B] (2), Cylinder O-Ring [AT276] (2), Retainer Screw [AT283] (4), Leaf Valve [AF817] (4), Piston Cup [AT280] (2), SKU: AES343