涉及的行业门类多，品种繁杂。2。 注重造型及外观工艺，结构简单，体积小。3。 使用简单，方便。
The 1 involves the industry category, species complex. 2 pay attention to the shape and appearance of technology, has the advantages of simple structure, small volume. 3 the use of simple, convenient.
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