A packaging for a reel of medical injection devices includes a base tray configured for supporting the reel and at least a first flat rib and a second flat rib. Each rib includes a respective slot arranged such that the ribs can be interlocked with one another by mutual engagement of the slots. The base tray includes at least two pairs of peripheral openings. Each opening is configured to receive an end of the ribs, so that the base tray and interlocked flat ribs engaging the base tray form a frame configured for enclosing the reel.