Holding Tank Vent Filter - Powered by our refillable Five-Chamber Carbon Helix™ (patent pending), the Nautilus Filter™ OEM dramatically increases air-to-carbon contact time, delivering over 5× the odor removal performance and lifespan of similar sized conventional holding tank vent filters. The Nautilus Filter™ OEM model is a perfect fit, drop-in, superior product replacement for other brands Dometic, SeaLand, SaniGard, YachtZMarine and others with the added benefits of the Carbon Helix™, Bypass Valve and its Refillable.