Graphite Grey Circle Round Air Vent Fit 100 to 150 mm Round Ducting Ventilation Cover Supply with Fly Net (Fly Screen / Anti-Insect Mesh). Heavy Duty. Simple To Fit. Ducting Ventilation Cover Fly Net Wall Ceiling with Fly Screen / Anti-Insect Mesh. Used as vents to rooms on the outside and inside of the building (basements, garages, drying rooms, and attics). Tough and Strong ABS Plastic. Easy, simple, and secure to fit.