"Sealand's new ECO filter marks the next generation of odour removal. Its new concave design allows more air to pass through the activated carbon and absorb more odours. Only fresh air comes out of the vent tube of the device. This new cartridge is made with 55% less plastic than the previous model. It is made of recyclable material, made of polyolefin (environmentally friendly). It fits perfectly and adapts to the same mounting brackets as the previous Sealand vent filter. It has been the first design change of the original vent filter since its inception more than 25 years ago. It has been proven to be 2.4 times more effective than other activated carbon filters. It absorbs odors from the tank throughout the boating season. The graph indicates the calculated capacity in grams of carbon disulfide that are adsorbed by each filter tested in the laboratory. Easily installed between the holding tank and the through-hull vent. Advantages: It doesn't matter what filter you have and what diameter it is. 16mm, 19mm, 25mm, 38mm. The Sealand Eco filter fits any holding tank, regardless of the size of the vent hose. Replaces previous Sanigard filters "