Weck Jars are an all glass jar and made in Western Europe.
They are the only jars certified safe for baking and microwave. The jars with straight side (cylinder, tapered jars) are also safe for freezing.
The lid is held in place with 2 stainless clamps and the seal is a natural rubber one. Take care when putting the clamps on the lids to stretch them on rather than snap them on which can cause chipping on the lid.