polyester mesh Avoid itching from mosquitoes, gnats and No-see-Ums Easy to mount and fast with magnet from inside, under 5 seconds. Even children can do it. No drilling and fixed installations. Thin, builds less than 3 mm. Suitable for hatches with interior dimensions up 12" x 12” (300 x 300 mm) and fits all brands. Enjoy your life onboard your sailboat or motorboat without mosquitoes or bugs. Keeps out mosquitoes, sand flies, No-See-Ums, gnats, flies, wasps etc.