Mega4 is part of Munchbox's range of interchangeable trays (when used with the Munchbox Maxi6 outer box), which includes four generously sized sections designed to suit a range of different food items, for those who want to pack bento-style, but like their snacks bigger than bite-sized!
NOTE: the compartments of each tray correspond exactly with the specially patterned silicone lid, which works to lock in moisture, preventing leaks, even between compartments. The patterns specific to each box and tray combination are what make it leakproof.
Mini4, Midi5 and Maxi6, Mega3 and Mega4 removable trays are interchangeable ONLY with the Maxi6 outer box. If you are unsure please ask.