holding the lenses in place bridge which connects the two eye wires chassis, the combination of the eye wires and the bridge top bar or brow bar, a bar just above the bridge providing structural support and/or style enhancement (country/Grandpa style). The addition of a top bar makes a pair of glasses aviator eyeglasses pair of brows or caps, plastic or metal caps which fit over the top of the eye wires for style enhancement and to provide additional support for the lenses. The addition of brows makes a pair of glasses browline glasses pair of nose pads that allows a comfortable resting of the eye wires on the nose pair of pad arms connect the nose pads to the eye wires pair of temples (earpieces) on either side of the skull pair of temple tips at the ends of the temples pair of end pieces connect the eye wires via the hinges to the temples pair of frame-front end pieces pair of hinges connect the end pieces to the temples, allowing a swivel movement. Spring-loaded flex hinges are a variant that is equipped with a small spring that affords the temples a greater range of movement and does not limit them to the traditional, 90-degree angle. Temple types Skull temples: bend down behind the ears, follow the contour of the skull and rest evenly against the skull Library temples: generally straight and do not bend down behind the ears. Hold the glasses primarily through light pressure against the side of the skull Convertible temples: used either as library or skull temples depending on the bent Riding bow temples: curve around the ear and extend down to the level of the ear lobe. Used mostly on athletic, children's, and industrial safety frames; Comfort cable temples: similar to the riding bow, but made from a springy cable of coiled metal, sometimes inside a plastic or silicone sleeve. The tightness of the curl can be adjusted along its whole length, allowing the back to fit the wearer's ear curve perfectly. Used for physically active wearers, children, and people with high prescriptions (heavy lenses). See the image of 1920s frames above. Materials Plastic and polymer Cellulose acetate Optyl, a type of hypoallergenic material made especially for eyeglass frames. It features a type of elasticity that returns the material to its original shape. Cellulose propionate, a molded, durable plastic 3D-printed plastic using super-fine polyamide