What does DOT lettering have to include?

Under 49 CFR 390.21, commercial vehicles over 10,001 lbs (or carrying passengers/hazmat) must display the carrier's legal name and USDOT number on both sides of the power unit, in colors that contrast sharply with the background, legible from 50 feet in daylight. Most shops spec 2" letters as the practical floor. Several states add their own numbers (TxDMV, CA number). Full guide: wraptor.app/blog/dot-lettering-requirements-guide.