Both types generally fall under 871610, which covers trailers and semi-trailers designed for housing or camping. The key criterion is the trailer's primary design purpose — accommodation — rather than its coupling mechanism. A trailer designed principally for cargo or equipment transport would fall under a different subheading even if it has some sleeping amenities.

Parts specifically designed for trailers and semi-trailers classify under 871690 within this heading, not under the general vehicle-parts chapters. The specificity rule applies: if a part is identifiable as suitable for use solely or principally with a trailer or non-mechanically propelled vehicle, it belongs here. Generic fasteners or materials that are not specific to trailers would classify by their own material or function.

Tanker trailers intended for use on US roads must comply with Federal Motor Carrier Safety Administration (FMCSA) regulations and applicable DOT standards for cargo tank construction. Depending on the commodity they are designed to carry (hazardous materials, food-grade liquids, etc.), additional agency requirements from EPA or FDA may apply. Classification under 871631 does not itself trigger a specific admissibility review, but operational compliance is required before the trailer enters service.