The EZ Flow II is made from heavy chipboard in a one-piece design. The filtering media is continuous filament spun glass and is made to function without a retainer, by adhering the frame directly to the media which has a light skin to make it self-retaining. A resinous bonding agent provides additional rigidity and resistance to media compression. UL Classified. Continuous filament spun glass filter media for residential and light commercial use MERV 1 rating Durable one-piece heavy chipboard filter frame Low initial pressure drop helps protect HVAC equipment reducing energy costs Lasts up to 30 days Available in 1" size