This General Ecology RS-1SG cartridge element is a replacement element for Seagull IV X-1 marine water purifiers. The high capacity, fast flow element offers chemical free water purification against chemical, microbiological and aesthetic contaminants. The RS-1SG element has an average capacity of up to 3800 litres (1000 US gallons) before needing to be replaced, however this capacity does depend on the quality and hardness of the water.