Worked well for my swamp cooler to prevent air leakage in winter.

This product is a square foam block 20"x20" with a sturdy fabric cover. It fits in the down vent below our rooftop evaporative cooler and blocks warm air from escaping during the winter months. Installation involves removing the vent diffuser in order to insert the plug. It really works well for the job for which it is intended.

Very accessible packaging. The fabric is very durable also washable. This should last years with the appropriate care. Seems very instalated so my heating cost do go up in the winter. Very affordable.