The primary enclosure must be strong enough to contain the animals securely and comfortably and to withstand the normal rigors of transportation.

The enclosure must be large enough that each animal has enough space to turn around normally while standing and to stand and lie in a natural position. Some species may be restricted in their movements when freedom of movement would constitute a danger to the animals or people.

Enclosure interiors must have no protrusions that could injure the animals.

For guinea pigs and hamsters, inner surfaces of fiberboard, cardboard, or plastic enclosures must be covered or laminated with wire mesh or screen where necessary to prevent escape.

Openings of the enclosures must be easily accessible at all times for emergency removal of animals.

Unless the enclosure is permanently affixed to the conveyance, adequate handles or handholds must be provided so that the enclosure can be lifted without tilting and to ensure that anyone handling it will not come into physical contact with animals in it.

Projecting rims must be on the exterior of walls that contain ventilation openings and provide a minimal air circulation space of 0.75 in.

Unless the enclosure is permanently affixed to the conveyance, it must be marked on top and on at least one side with the words “Live Animals” or “Wild Animals” in letters at least 1 in high and with arrows indicating the correct upright position of the enclosure.

A solid, leakproof bottom that prevents seepage of waste products outside the enclosure is required. Unless it is on a wire or other nonsolid floor, the enclosure must contain enough unused, nontoxic litter to absorb and cover excreta.

The primary enclosure must be cleaned and sanitized before each use.

The interior height and space per animal of each enclosure must comply with the following minimal standards for guinea pigs and hamsters (there are no minimal requirements for rabbits and other animals):