Lennox Healthy Climate HCC20-28 Healthy Climate True Fit HC16 filter cabinet - X6661. Filter dimensions: 20" x 25" x 5".

The Lennox X6661 Healthy Climate HC20 Cabinet is the #1 rated professionally installed, whole-home filtration system as ranked by a leading consumer magazine, it provides whole-home filtration for optimal home comfort and air quality, with no additional energy costs.

The Lennox Healthy climate HCC20-28 Healthy Climate True Fit HC 20 filter cabinet does NOT come with a filter, you will need to order that seperately. Here are the recommended filters for the Lennox Healthy Climate HCC 20-28 Healthy Climate True Fit HC20 filter cabinet:

Lennox MERV 16 filter media as well as some MERV 10 filter options.
The Lennox X8788 MERV 16 filter is the replacement for this Lennox HCC20-28 cabinet.  (X8788 Dimensions: 20" x 26" x 5" Actual: 20" x 25-1/2" x 4 3/8")

There is also an "expandable" pop up filter kit available in a MERV 16 option - Lennox X8307.
For the MERV 10 options: Lennox X6673 MERV 10 filter, or the Lennox X8304 "expandable" pop-up filter, are  suitable replacements for this Lennox HCC20-28 cabinet.