The first filter is a pre-filter that helps remove soap, oil, and other suspended particles before they enter the filtration system. It reduces the need for chemical additives such as clarifiers, scum removers, cleaning agents, and defoamers, minimizes filter maintenance, and helps maintain clean water. 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: The spa pre-filter can be rinsed as needed. It is recommended to clean it weekly and replace it every three months depending on usage and spa conditions. Compatibility: This replacement pre-filter is designed for use in spas and is compatible with Maax, LA Spas, Cooperage, and Elite Spas models. Color: White Material: Chemical Fiber Package Contents: 4 x First Filter Note: Light reflection and differences in display screens may cause slight variations in color between the product and the image. Measurement may vary by +/- 1-3 cm.