Filter cartridges keep the water in your hot tub clean. They are easy to install and maintain. They just require regular rinsing under the tap. However, if they remain dirty or discoloured after rinsing, they must be replaced. Otherwise, the filter pump may get damaged. Mspa filters are not made from paper, but polypropylene: a sign of quality and longevity. Dimensions: 11.5x8.6cm (4.5" X 3.4"). Suitable for MSPA Alpine/Silver Cloud/Reve/Soho/Exotic/Camaro/Tuscany/Mono/Carlton/Otium/Aurora/Nest/Rimba/Vito MUSE / FRAME collections. Only 2 Filter Cartridges Supplied. Shatchi Pack of 2 Hot tub - 120 Pleats Filter Cartridge, Twin Pack all hot tubs in Blue