Check the listing for details. 3 Pack 313 Replacement Air Filter Compatible with AprilAire 313 20"x20"x4". Condition: New. Listed at 10.00 USD. Protecting Your Whole Home: Upgrade your air purification system effortlessly with the Riverline 313 Filter Replacement tailored for Aprilaire Models 1310, 2310, 3310, 4300. Our aftermarket filter is engineered to elevate performance while simplifying installation, ensuring cleaner air with ease. Unique Magnetic Design (Patent Pending): The Riverline filter features two plastic end caps with strong magnets, ensuring the filter stays securely attached in an upright position to the metal unit. This innovative design offers a significant improvement over traditional filters. This filter is specifically designed for units installed in a vertical position. If your unit is installed horizontally, we recommend not purchasing this