Glass is the oldest, and most familiar, performance fiber. Fibers have been manufactured from glass since the 1930's. Although early versions were strong, they were relatively inflexible and not suitable for many textile applications. Today’s glass fibers offer a much wider range of properties and can be found in a wide range of end uses, such as insulation batting, fire resistant fabrics, and reinforcing materials for plastic composites. Items such as bathtub enclosures and boats, often referred to as “fiberglass” are, in reality, plastics (often cross linked polyesters) with glass fiber reinforcement. And, of course, continuous filaments of optical quality glass have revolutionized the communications industry in recent years.