System of open-topped containers

A system of containers, the system comprising:

• at least two alternately vertically stackable open-topped male and female containers that each comprise a single continuous structural unit, so that within a stack a male container meets a female container and vice versa,
• each male container comprising:
• a substantially rectangular bottom having an upper surface, a lower surface and an outer edge of each side thereof
• two pairs of oppositely located side walls extending from the bottom, each side wall having a rim disposed at an upper end of each side wall, the rims of the side walls being interconnected to form an opening, the lower end of the side walls being interconnected with the bottom at an inwardly position from the outer edge thereof, at least a portion of the outer surface of each of the side walls of the male container extending angularly inwardly from the bottom towards an opposing side wall such that a distance between rims of each pair of oppositely located side walls is smaller than a distance between the lower ends of each pair of oppositely located side walls, and
• each female container comprising
• a substantially rectangular bottom having an upper surface, a lower surface and an outer edge of each side thereof,
• two pairs of oppositely located side walls extending substantially vertically from the bottom, each side wall having a rim disposed at an upper end of each side wall to form an opening, and
• wherein, when the female container is turned by 180° from an upright position, the walls of the male container will fit within the opening of the female container.