A container, system, method, and computer readable storage medium, for monitoring at least one of surgical object and fluid placed into the container are provided. The container includes a rigid top member including at least one port opening therein, having a recessed portion of the underside of the top member along an outer perimeter, a rigid retaining ring sized and shaped to match the size and shape of the recessed portion along the outer perimeter, and a flexible bag body having an open top portion and a sealed bottom portion, an outer perimeter of the open top portion being folded over the rigid retaining ring, the rigid retaining ring with the folded over perimeter of the open top portion of the flexible bag body being mated and locked in the recessed portion of the underside of the rigid top member along the outer perimeter in a fluid-tight seal arrangement.