Mich. Comp. Laws § 570.565

Sec. 25. To enforce a lien that attaches under section 23, the special tool builder shall give notice of the lien in writing to the customer and the end user. The notice shall be given by hand delivery or certified mail, return receipt requested, to the last known address of the customer and to the last known address of the end user. The notice shall state that a lien is claimed, the amount that the special tool builder claims it is owed for fabrication, repair, or modification of the special tool, and a demand for payment.