Wasps, mud daubers, birds, and rodents pose a serious threat to the furnace on your RV. They can enter through the furnace vents and cause serious damage by building nests that interfere with air flow. The Camco Model FUR 300 Flying Insect RV Furnace Screen fits Atwood Hydroflame furnaces that have an access door. This easy-to-install screen will help ensure that your furnace vent stays free from costly invasion by unwanted pests.• Screen measures 4-7/8" x 4-1/2" x 1-1/8"• Fits Hydroflame furnaces with access door series furnace vents• Protects the furnace from flying insect nests• Easy to install â just drop in place and close cover• Heavy-duty stainless steel mesh cover Heavy-duty stainless steel mesh cover Just drop in place & close cover to install Screen measures 4-7/8"" x 4-1/2"" x 1-1/8"" | Camco Flying Insect Screen for Hydroflame 8500 Furnace Vents