Astral ZX Cartridge Filters are a compact design. As a backwash line is not a requirement it makes ZX Cartridge Filter model the perfect solution for situations where water restrictions are enforced and / or if space is an issue. Australian made with quality products the ZX filters come in a range of sizes. If you need assistance sizing a cartridge for your pool please contact us. The ZX Cartridge filter is complete (housing and filter).