This humidifier filter is designed to prevent growth and migration of mold, fungus, algae. It is made of high-quality wood pulp paper, very safe and healthy to use. 2 types humidifier filter could be for you to choose to match your humidifier, HU4101 is suitable for HU4901/HU4902/HU4903, HU4136 is suitable for HU4706/HU4701/HU4702/HU4703. Specifications: Material: Wood pulp paper Color: White Type: HU4101, HU4136 (Optional) HU4101 Suitable for: HU4901/HU4902/HU4903 HU4136 Suitable for: HU4706/HU4701/HU4702/HU4703 Usage: Water filtration Lifespan: 1-2 years Aperture Ratio: 90% HU4101 Size: Approx. 26 x 14 x 4cm / 10.2 x 5.5 x 1.6inch HU4136 Size: Approx. 13 x 16 x 4cm / 5.1 x 6.3 x 1.6inch (Shown as Picture) Weight: Approx. 45g-80g Package Included: 1 x Humidifier Filter Replacement HU4101 used for HU4901 / HU4902 / HU4903 HU4136 used for HU4706 / HU4701 / HU4702 / HU4703 Used to prevent the growth and migration of mold, fungus in the filter. Easy to use and simple to install, adopts high quality wood pulp paper. Humidifier Filters used to Protect treated filter inhibits up to 99% of mold growth and removing minerals from water.