Long lasting, strong, and durable, these are just a few words to describe our line of Glasfloss ZL 4 Inch pleated HVAC filters. Utilized for residential, commercial, industrial, healthcare, and other building filtration requirements. Manufactured for difficult air flow environments in mind, the four Inch filters are recommended by HVAC technicians nationwide. With our fast free shipping service, our customers save on cost, but get improved convenience and trustworthy quality.