The first filter is a pre-filter that helps remove soap, oil, and other suspended particles before they reach the main filtration system. It reduces the need for chemicals such as clarifiers, scum removers, cleaning agents, and defoamers, minimizes filter maintenance, and helps maintain water cleanliness. Easy to Install: Place the hot tub pre-filter on top of the skimmer basket. Secure the filter tab into the existing slot of the MAAX Spas skimmer basket. First filter model number 100497. Easy to Clean: This spa pre-filter can be rinsed as needed. It is recommended to clean it weekly and replace it every three months, depending on spa usage and condition. Compatibility: This replacement pre-filter is designed for use with spas from MAAX, LA Spas, Cooperage, and Elite Spas. Color: White Material: Chemical Fiber Package Contents: 4 x Pre-Filter Note: Light reflection and differences in display screens may cause slight variations in color between the product image and the actual item. Measurement may vary by +/- 1-3 cm.