Without prejudice Dear …

RE: Patent #__(reference #)__ - __(type of product)__

Please allow this letter to serve as an official written notification that Patent # __(#)__ has been issued to __(name of person or organization)__ for the __(invention/design/etc.)__ of the following product:

__(description of product)__

Reproduction of the above mentioned product, without express or written permission by the Patent owner, is strictly prohibited. The full intent of this notification is to bring to your attention that any unauthorized reproduction of said product is deemed to be illegal, and will not be tolerated. Further, please be made aware that any and all offenders of such illegal action, without exemption, will be prosecuted to the fullest extent of the law.

Please consider this your one and only warning.

Yours truly,