Sogeman Microlog ME1822 Bugbusters hatch insects screen, 18" X 22", 100% Mil Spec Polyester mesh, lead ballasted (will not affect compass), stows in a strong plastic carrying case. These screens are a simple solution for no-see-ums, mosquitos and other bugs. Installation is a cinch, just put the Bugbusters over the hatch and the generous dimensions allow the hatch to open fully from inside for maximum ventilation. Installs instantly over any hatch. No attachments necessary. Allows easy adjustment of hatch opening from inside. To measure just close the hatch, take measurement and add 10 to 20% extra size to fit neatly. Example: 16" x 20" hatch would use a 18" x 22" screen.