The Dial 8303 31" x 9" x 27" Side Swamp Cooler Cover for your evaporative cooler is not easily penetrated by water and made of rot resistant materials that prevent bio-degradation. It has durable brass grommets with draw-rope to secure the cover to the cooler with heavy duty sun-resistant cord. Dial 8303 Side Swamp Cooler Cover also features UV resistant capabilities through being fully coated with polyurethane that prevents damage during tough weather conditions. This evaporative cooler cover offers a waterproof and breathable material that will not let water vapor through. That being said, it is constructed of polyester fabric that is extremely rugged making it last longer than canvas. The cover is slightly larger than the evaporative cooler that it will be used for. The slightly larger size allows for shrinkage of the cover due to use and weathering. Overall, Dial 8303 Side Swamp Cooler Cover prevents corrosion and extends your evaporative cooler life. Should you need anything for your evaporative coolers, www.plumbersstock.com is your trusted buddy in any cooler replacement components, supplies and tips.