A PVSIS2 vent screen at https://pvcventscreens.com/product/pv... was used to replace a recently installed furnace vent screen that already had a wasp nest being built inside of it. The PVSIS2 vent screen is designed to protect furnace intake and exhaust vents during spring, summer and fall. During winter, when insects are not active, the PVSRS2 vent screen should be used inside 2" PVC furnace vent terminations having an inside diameter of 23/8". When used as intended, the PVSIS2 and PVSRS2 vent screens provide complete allseason vent protection to protect vents from bees, wasps, birds, rodents and debris. The PVSIS3 and PVSRS3 vent screens are designed to fit inside of 31/2" vent terminations, which are also commonly used for residential high efficiency furnaces. For optimal performance, a licensed HVAC technician should inspect your furnace and ventilation system annually.