This 48"W x 30'H filter is made using extra heavy weight polyester fibers bonded into a tough, durable air filter media. Fibers are formed into a high loft, interlocking mat. Inherent rigidity eliminates need for external support, yet flexible enough for easy installation in tight spaces. Can be easily vacuumed or rinsed off with water and re-installed for low maintenance and cost effectiveness. UL listed.