DOT Certification Logo – The DOT-C2 designation is to appear on the tape at least every 12 inches. The characters should be at least 3 mm tall and stamped in indelible ink or an equivalent. The exact wording is below:
S5.7.1.5 Certification. The letters DOT-C2, DOT-C3, or DOT-C4, as appropriate, constituting a certification that the retroreflective sheeting conforms to the requirements of S5.7.1.2, shall appear at least once on the exposed surface of each white or red segment of retroreflective sheeting, and at least once every 300 mm on retroreflective sheeting that is white only. The characters shall be not less than 3 mm high, and shall be permanently stamped, etched, molded, or printed in indelible ink.