Ophthalmic grade plastic is used in the majority of all major brand sunglasses. Excellent quality, easy to adjust, holds its color well.
Temples have a reinforced metal core.
These frames have strong hinges either molded into the frames, or secured by rivets. Acrylic is available in both tinted and mirrored lenses, and is also used clear, for reading glasses and goggles. Most often found in top-quality sports glasses. It is Lexan from G.E., the same material used for bullet resistant glass in autos. It is such hard material that a special diamond grinding wheel must be used to cut the lens.