Pentair Square Spa Skimmer Weir Door with Foam (550-4051) valterraproducts A lid assembly like this

A lid assembly like this is useful because it helps secure the tank while also supporting the top-side flow-control function built into the unit

Use this part when the original label is missing

this MasterTemp/Max-E-Therm O-Ring Kit [After 1/12/2009] is built for that role

A kit like this is useful because it restores the primary temperature-reading component and the safety-related Temp sensor in one service package

Pentair Square Spa Skimmer Weir Door with Foam (550-4051) valterraproducts A lid assembly like thisThe Waterway Square Spa Skimmer Weir Door with Foam is a replacement skimmer component for compatible square spa skimmer assemblies. The weir door helps improve surface skimming by controlling water movement into the skimmer opening, while the foam helps the door float and respond properly as water level and flow conditions change. A damaged or missing weir can reduce skimming efficiency and allow debris to drift back into the spa. Replace this part