1. Do the grills rattle? As part of our assembly process, the slats go through interlocking center bars, which give the grills excellent stability and dampens any tendency of the slats to vibrate. 2. Is there sufficient air flow? Yes, if the grill is sized correctly. Our wood grills have approximately 12% less clear area when compared to the same size metal grill. 3. Can they be installed in existing openings? Yes, if the opening is large enough. In some cases changing out the same size grills, wood for metal, you may need to make some alterations. The wood grills require the openings to be ¾" wider and ½" higher than the grill size (which is also the filter size).