The first filter is a pre filter before the main filter,which filters out soap,oil,and other suspended particles before they reach the main filter. It helps to reduce the use of chemicals such as clarifiers,scum removers,cleaning agents,and defoamers,minimizing filter cleaning and maintaining water cleanliness. Easy to Install: Place the hot tub first filter on top of the skimmer basket.Lock the first filter tab into the existing slot MAAX Spas skimmer basket. First filter model 100497 number 100497. Easy to clean: The first filters for spas can be cleaned according to your condition,it is recommended to wash it once a week.Replace it according to the condition of your spa, it is recommended to replace it once in three months. Application: The first filter replacement is suitable for Coleman spas, for Maax, for LA Spas, for California Cooperage, for Elite Spas. Colour:White Material:Chemical Fiber Package Contents: 4 x First Filter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is 1-3cm.