1. composition: water shell gold is a kind of gold with high purity, containing only a small amount of other metals; 999 gold is thousands of pure gold, which is the highest value in jewelry color naming.

2. Purity: the purity of water shell gold is high and the impurity content is low, so the color is bright and the texture is soft; The purity of 999 gold is not lower than 999, so it is also called "thousands of pure gold", which is the highest value of jewelry fineness in market circulation.

3. Price: Due to the high purity of gold in water shell, its price is also higher than 999 gold, and the price of gold in water shell per gram is twice that of 999 gold.