A carrier unit adapted to be converted into a bulk material carrier generally including a container having a floor, the floor having at least one floor section movable to a selected position providing a surface inclined toward an opening in the floor formed by the removal and positioning of the floor section into the selected position, a pair of wall units disposed within the container, movable between storage positions and operative positions on opposite sides of the floor section to cooperate with the floor section in the selected position and portions of the interior walls of the container to define a compartment, and a flexible liner for holding bulk material, mountable in the compartment, the flexible enclosure having an inlet for charging bulk material thereinto and at least one outlet cooperable with the floor opening for communicating the interior of the flexible liner with the exterior of the container.