Tank specification "MC-306" or "DOT-406" generally refers to:
Correct. MC-306 (older) and DOT-406 (current) are non-pressure cargo tanks for flammable and combustible liquids — typical fuel tankers.
CDL Practice Question #333
Category: Tanker
Why this question matters
This question is one of 50 in our Tanker bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.