The first filter is a pre-filter that traps soap, oil, and other suspended particles before they reach the main filtration system. It helps reduce the need for chemicals such as clarifiers, scum removers, cleaning agents, and defoamers, minimizes filter maintenance, and supports 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: This 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: Designed as a replacement for spas by MAAX, LA Spas, Cooperage, and Elite Spas. Color: White Material: Chemical Fiber Package Contents: 4 x Pre-Filter Note: Light reflection and display settings may cause slight color variations between the image and the actual item. Measurement may vary by +/- 1-3 cm.