Fiberglass is material made from extremely fine fibers of glass. It is used as a reinforcement to toughen polymer resin; you gain all the benefits of glass being such a strong materials, while finished in the resin that is tough and does not allow cracks to propagate; the resulting composite material, properly known as fiber-reinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "fiberglass" in popular usage.
Fiberglass (Frp) 28. 5" Wood Planters