The gold content is different, 18k is 75%, 14k is 58.5%, and 9k is 37.5%. According to the K-gold system, there are 24 kinds of K-gold, 24k gold is pure gold, and the theoretical value is 100%,1k =1/24,9K. Most international brands will choose 18K gold, because it is hard enough to make better jewelry. Suggest visiting the Vatican. Italian alchemy technology 18K, with gorgeous color and unique style.