Whereas the filter material itself seems fine, the box for it (e.g., Lennox X6661) leaves to be desired. When you make a MERV 16 claim, leakage around the filter matters a lot. There are multiple opportunities for air to leak into the return and for air to bypass the filter. There are:
-Holes in the corners
-Uneven mounting surfaces (both sides of the box -- one would need to apply caulking all around during installation to seal it off. Of course the installation instructions don't suggest doing that)
-large tolerances (for a MERV 16 filter) between filter and box, and no gasketing around the top and incoming or outgoing sides of the filter
-The "gasketing" that is present is open cell foam and also what looks like a pad of fibers with a low MERV rating, through which air can flow. Air can leak into the return as well through the open cell foam. The foam is in multiple pieces with small gaps in-between.
The box looks great, is practical, and would be adequate for a MERV 6-8 filter. However, it can't possibly come anywhere close enough to be able to support a MERV 16 filter. I'm disappointed, although not entirely surprised.