The 4 oz clear containers are made from PET.  


The white lids are made from Polypropylene. They are dishwasher-safe.


Both are BPA-free and BPS-free and do not contain any additives, fillers, or phthalate plasticizers.


Both materials are also recyclable. Check with your local recycling curbside recycling programs as not all programs except #5 PP (lids).  


We love these containers because they are sturdy and reusable.  Give them a quick hand wash and reuse for other snacks or baby meals. 


They are shatter-resistant, which we felt was safest for a frozen food shipped with dry ice.