"Perennials® and Sunbrella® fabrics are 100% solution-dyed acrylic. All our fabrics resist stains, mildew and fading, making them easy-care and weather-friendly. Perennials® fabrics will pill over time. This is a natural characteristic of the fabric and does not indicate a defect. If desired, a light pass over the surface with a fabric shaver will remove any raised fibers, creating a smoother appearance without affecting the structural integrity of the fabric. Although our outdoor upholstery fabrics are mildew resistant, spores that create mold and mildew thrive in environments with dirt and moisture. To deter mold and mildew, always remove wet cushions from furniture frames and perform frequent cleaning and maintenance." OD_CareSheet_Upholstery_en-US.pdf (restorationhardware.com)