NoSeeUm Insect Window Screen is A finer mesh fiberglass screen to protect against noseeum, gnats, sand flies, and other tiny insects common in low marshy and coastal areas. Is also Heavy Duty Mesh suitable for Patio, Porch and Pool Enclosures. Charcoal color only. Mesh: 20 x 20, Diameter: .013. Charcoal NoSeeUm Fiberglass Screen