* Below poor performance at filtering 0.3-1µm particles, which are more likely to lead to chronic lung-related conditions.

* OK performance at filtering 1-3µm particles, which are more likely to cause various respiratory problems and other health and productivity issues.

* Below mediocre permeability. The lower the permeability score, the more strain the filter would put on your equipment which can dramatically increase the cost of operating your furnace, air conditioner, or heat pump (and potentially damage it).

* Requires an aftermarket filter housing which could potentially require a professional installation.

* High maintenance. Clogs fast.

* Lower MERV rating than advertised.