Dear Mr. Glaze,

I would like to take this opportunity to thank you for your filter services for both air conditioning units in our building. The filters that you use must be of higher quality than any I have purchased in the past as I have noticed a significant change in the amount of cooler air being produced by these units. Also, the electric power bill reflects a savings.

The service that you provide is certainly reasonable and I would recommend your service to anyone using air conditioners or heaters. Keep up the good work and, once again, thanks.

Sincerely,
Professional Graphics, Incorporated