Brilliance plastic is a hard crystal clear plastic that looks like glass but isn’t heavy or breaks easily like glass. The lids have rubber seals for airtight and leak proof. It easily snaps on and off and has holes for venting. They stack neatly for easy storage. It is BPA free, microwave safe, freezer safe, & dishwasher safe on top rack. This is by far the best to-go container. I have to buy more because everyone prefers it over the regular containers. FYI, 3.2 cup size is what we use to pack lunch. Roomy enough if you eat less or just right if you eat a little more.