Fiberglass is a material made from fine fibers of glass and it’s advantage is that it can be recycled and has been for decades according to the Modernica’s website. Unfortunately, DWR discontinued making the chairs with this material with instead using polypropylene. I personally feel that fiberglass gives more charm to each chair because none of them has a same texture on the surface. Below is a video from Modernica about the process of making them!