It's no secret. Insects, rodents and birds like to build nests in out-of-the-way places, including in RV water heater, furnace and battery compartments. Don't let it happen to you. Safeguard your RV's compartments by installing a CAMCO Flying Insect Screen. Measuring 4.5 x 4.5 inches, the sturdy mesh wire screen will keep pests out and maintain quality airflow in and out of your RV water heater, furnace and battery compartments. The screen is easy to install and comes with complete step-by-step instructions.