Prefabricated memory plastic cubicle
From Halopedia, the Halo wiki
Prefab Memory-Plastic Cubicles are small, one-person, structures meant to provide shelter to UNSC troops in the field. Like the 'archaic' tents they replaced, cubicles are collapsible and man-portable. Understandably, more comfortable accommodations are substituted for Cubicles whenever possible.
Cubicles were used extensively at Alpha Base on Installation 04. Having abandoned the UNSC Pillar of Autumn aboard HEVs, the ODSTs were forced to rely on cubicles stored in their drop pods.