The 360° cylindrical filter is designed for maximum intake. The triple-layer filter uses a primary filter, Toray H11-grade HEPA filter and activated carbon filter to remove dust, odours and other respirable It is made with PET (polyethylene terephthalate), the outer layer has high flexural strength and is resistant to folding, grease, fats, acids, alkalis and most solvents. The cylindrical shape provides 360 degree filtration of dust, hair and other larger floating particles. Typical air purifiers require you to change filters layer by layer. Mi Air purifier simplifies this by integrating all three layers. Simply pull out and push in. It's that easy.