Z-Line 500 AB (Air Bear ) and 300 AB (Air Cub ) : These pleated filters are an ideal replacement option for the Trion Air Bear® and Air Cub® filters. The Z-Line 500 AB and 300 AB filters incorporate 100% synthetic fibers that are thermally-bonded, and manufactured in an engineered gradient structure. Z-Line 500 AB and 300 AB filters achieve a MERV 10, MERV 11 or MERV 13 rating when tested in accordance with the ANSI/ASHRAE 52.2 Test Standard. Pre-applied gasketing on the top and bottom of the filters help prevent air bypass. No modification to the filter frame is necessary. The Glasfloss 500 AB and 300 AB filters are available with activated carbon to absorb unpleasant household odors. Refer to Z-Line 500 ABX and 300 ABX when ordering. Each filter is sealed in plastic to avoid contamination before use.