You are buying purity and quality. 18 carat gold chain 7.2 gr weight, 20 inch long, 5 mm. Why to buy an 18 caract gold chain? *Pros and Cons: 18K Gold vs. 10K and 14K Gold Compared with lower karat gold, 18K jewelry has some distinct advantages. since it is purer, it is less likely to cause an allergic reaction in people sensitive to nickel, if this metal is present in the alloy. A 10K gold piece that contains nickel, on the other hand, is more likely to give you a rash if you are allergic to the metal. Another upside to buying 18K gold is that its color is closer to that of pure gold, while the yellow in 10K or 14K jewelry may not be as intense. * Jewelry notes