Clarathon Premium Ultra Filters are the most effective and durable pool and hot tub spa filter cartridges available. In fact, you cannot buy a better quality filter at any price. Tips: Keep spares on hand. When you change your spa water, always rotate the soiled filter out with a clean, dry spare. The result is longer filter life and no waiting. These Money-saving reusable Microban­® Antimicrobial replacements for Master Spas Eco Pur mineral inner filter promote clean, clear spa water. Use with a conventional or mineral spa sanitizer system.