There are hundreds of types of frames, and the one you pick for your eyeglasses will probably depend on several factors, including medical, cosmetic, and cost. The shape of your face, skin tone, hair color, clothing, and lifestyle are other factors to consider. Frames can be made of plastic, metal, or nylon. Plastic is easy to mold, less expensive, and is available in a variety of translucent and opaque colors. The disadvantage is that plastic frames are more breakable than metal ones, although they can last if handled with care. Metal frames are made of aluminum, stainless steel, titanium (tie-TAY-nee-un), or beryllium (buh-RILL-ee-um). Beware of metals that are very inexpensive, because they may lack durability. Nylon frames are used mostly in sports and safety glasses. Although the frames are virtually unbreakable when new, they can lose moisture and can become brittle with age. In general, the quality of frames is evident in the material used, workmanship, attention to detail, and the integrity of the hinges and nose pads. Styles change in frames as they do in clothes, jewelry, and other items you wear. Many frames now carry the names of fashion designers. Some designers have knowledge of the product, while others have just sold their name and let the frame manufacturer have total control. If your lenses require a lot of correction, you'll generally need a smaller frame. The larger the lens, the thicker it must be, and it may not fit well into a larger frame. Choose a frame to fit the shape of your face. An oval face is balanced vertically and horizontally, so most frame styles will be complimentary. If your face is round, the most flattering frames are angular, such as rectangles, squares, or other geometric shapes. A heart-shaped face that tapers to a narrow jaw line looks best with a frame that sits low on the temples, while a square-shaped face is flattered by a frame with high temples.