It made of polyester, the ac cover's elastic edges and pvc-lined stitching allow the edges to stay securely gripped preventing it from slipping. Using the quality polyester material allows for your heat to stay inside and the drafts and winds to stay outside of the window. The indoor air conditioner cover with embedded cotton blocks warm air escaping and cold air getting through in AC, prevent heat loss in the winter to reducing heating costs. The inner lining near the air conditioner is made of water-resistant fabric, block humid air entering to keep your equipment safe and the hole in the bottom corner allows the cable to pass through.