Premium airtight plastic containers? Stable stacking available with Modular type system? Various composition from small to super large capacity for different kinds of foods? Airtight container with safe material which is Bisphenol-A free ? Rectangular/square shape for economical space use storage (Microwave ,Disherwash,Freezer)-Save.Microwave and Freezer Use & Care:* Do not microwave empty containers. Be sure to open the lid when microwaving. Use it only for heating up foods high in fats oils as containers can be stained or deformed. When microwaving foods low in water, do not heat it for more than 2 min. After keeping it in freezer for a long time, the hinges can break if opened immediately. Wait 1~2 minutes and open it.