Airfoil’s Perforated Return Air Grille combines a lightweight core of perforated aluminium plate. This grille has a free area of approximately 50% which makes it extremely effective in supply and return air functions. Airfoil’s Perforated Face Tamperproof Grille is manufactured to the highest standard providing utmost security. The outer frame is folded from 0.75mm zinc anneal for maximum strength and rigidity. The centre core is removable for ease of installation and is held in place by tamperproof security screws.