Some of the 2 tier bento boxes in our catalog comes with an inner polyethylene lid. These are not microwave safe. These replacement lids are for any damaged or lost inner lids. Please take note of the correct lid for the correct bento box. Which lids for which bento box? Rectangle inner lid: Benkei 2 tier big bento box Oval inner lid for 380ml compartments: Sakura Usagi Pink 2 tier bento box, Sakura Usagi Red 2 tier bento box, Kimono Yume Sakura Pink 2 tier bento box, Kimono Sakura Blossoms Oval 2 tier bento box Oval inner lid for 450ml compartments: Hinoki Nuri Wappa 2 tier bento box, Urushi Nuri Wappa 2 tier bento box Product details Made in Japan Material: Polyethylene Temperature tolerance range: -20°C to 60°C Weight (Rectangle): 40g Weight (Oval for 380ml compartments): 26g Weight (Oval for 380ml compartments): 30g Not microwave or dishwasher safe