FMVSS No. 108

FMVSS No. 108, "Lamps, reflective devices and associated equipment", sections that include the labeling requirements.

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.

S5.7.2.3 Certification. The exposed surface of each reflex

reflector shall be marked with the letters DOT‑C which constitutes a

certification that the reflector conforms to all applicable requirements

of Sec. 571.108 of this part. The certification shall be not less than 3

mm high, and permanently stamped, etched, molded or printed in indelible

ink.