12" x 36" NoSeeUm" Fiberglass Insect Screen in Charcoal, weave is a tight 20 x 20. This Screen is used for keeping the tiniest insects out of your house, tent, patio. We use it to keep the tiny Melanogaster inside the Mantis containers. Most window screening do not keep these tiny insects inside where you want them. It is a fiberglass material and will not rust, is easy to clean, and strong. Size 12 x 36"