Nailor 51PR, 61PR, and 67PR Series Perforated Grilles and Registers feature a high free area perforated face and is available in a choice of aluminum, steel or stainless steel construction. Their general appearance matches and compliments the Nailor 4300 Series Perforated Supply Diffusers. Optional roll-formed steel opposed blade damper has a removable key operator or screwdriver adjustment through the face of the register with a special access hole.