The 4-layer expansion function of the Symphony Electroplating Powder Box may include

Outer box: External packaging box, usually used to package and display powder boxes, may contain brand logo, product information, etc.

Lid: The lid of the powder box, used to cover and protect the cosmetics inside the powder box, and may have a mirror or other accessories.

Base: The bottom part of the powder box, used to hold cosmetics. It can usually be opened or disassembled for easy access to cosmetics.

Compartments: Some powder boxes may be designed with compartments to separate different types of cosmetics or to place makeup tools such as powder puffs.

These layers of design can make the powder box more practical and easier to use, while also helping to protect cosmetics and enhance the appearance and texture of the product. Specific product designs may vary by manufacturer and product type.