The frame materials of sunglasses are roughly divided into three categories: metal, resin, and composite plates. Of course, there are many subdivisions within these three categories. When purchasing, you should mainly look at its weight, strength, flexibility and other indicators. Among the metal materials, titanium alloy has the best quality but is also the most expensive, aluminum-magnesium alloy has the second highest quality but is slightly more expensive; among resin materials, TR-90 has good flexibility and wear resistance, but is slightly more expensive.