For Mspa Hot Tub Filter Cartridges. The filter cartridges keep the water in your hot tub clean. They are easy to install and maintain. All you need is regular rinsing under the tape. If they retain dirt or disperse it after being glued, they must be replaced. Otherwise the filter pump may be damaged. Product features: Colour: grey, white. Material: polyester. Dimensions: diameter 11.6 x 6.7 cm. Box contents: 4 filter cartridges without cover. Note: 1. To maintain the operating performance of your filter , we recommend changing the filter cartridge every 2-3 weeks depending on usage. 2. Due to the light and screen difference, the item's color may be slightly different from the that of the picture.