Protect your unit from flying insects with the Flying Insect Screen for Duo-therm, Durotherm, and Suburban furnaces. Wasps, mud dauber nests, birds, and rodents pose a serious threat to your RV water heater, furnace, and stove. They can enter through vents and openings and cause serious damage by building nests that interfere with air flow. Protect your valuable investment by purchasing and installing a flying insect screen. These easy-to-install screens will help ensure that your vents stay free from costly invasion by unwanted pests. Easy to install | Camco Flying Insect Screen for Duo-therm, Suburban and Durotherm Furnaces