The shell of electronic products in several materials?

How many materials are used in the shell of electronic products? Electronic products shell sets of materials generally use stainless steel, aluminum alloy and plastic more;

But the aluminum alloy molding time is long, the appearance of stupid thick, metal texture is poor; and plastic is low strength, do not drop, easy to dirty,

Sound quality is poor. Foshan Gangzheng stainless steel has a simple process, short construction period, metal texture, thin wall, sealing, good sound quality and so on,

So stainless steel is the future trend.