Valterra's A10-1302VP Bug Screen for Outside RV Furnace Vents are designed to fit Atwood Hydro flame 8500 Series furnace vents. They are easy to install and offer minimal airflow restriction while ensuring that your vents stay free from costly invasion by unwanted pests (nesting insects, birds, and rodents). An installation tool and two spring fasteners are included with each bug screen. Screens should be inspected monthly and cleaned when necessary to maintain proper air flow. Screen measures 4. 5" x 4. 88" x 1. 3".