Before using a filter rated MERV 9 or higher, you may want to have an HVAC technician check your central system to be sure it can handle any added airflow resistance that higher efficiency filters may cause. Check the compatibility and documentation provided by the manufacturer to avoid any potential issues. Specifically, Eljer makes and sells plumbing and HVAC products in the United States and Canada and HVAC products in Europe. They are usually black like the abs drainpipe but they may be chrome too, about 4 inches long, closed at the top with slots for air around the bottom, and around the same diameter as the plumbing pipe they are attached to. The letters in the marking must be: (i) At least 12 mm (0.5 inch) in height on packages having a gross weight of more than 30 kg (66 pounds); or (ii) At least 6 mm (0.25 inch) on packages having a gross weight of 30 kg (66 pounds) or less, except that smaller font may be used as necessary to fit package dimensions; and (2) The provisions of paragraph (a)(1) do not apply to packages that contain 5 kg (11 pounds) net weight or less of primary lithium batteries or cells that are contained in or packed with equipment and the package contains no more than the number of lithium batteries or cells necessary to power the piece of equipment; b.