A: In international trade, buyers and sellers usually live far from each other, which can give rise to a problem. The buyers can not examine the quality of the imported goods. Therefore there needs to be some ways for the sellers to inform the buyers of the quality. In international trade, sales by sample, sales by trade mark or brand, sales by specification, grade or standard and sales by description, these four means are generally used to express the quality of products.
　　B: Yes, through the sample, buyers are able to know the quality of the products. A sample is a small quantity of the products but represents the whole.
　　A: Sales by trademark or brand are normally useful to the products that have already obtained export markets whose brands or trade marks are already widely known.
　　B: Ok, sales by specification, grade or standard are another means to display the quality of the products, namely, through certain recognized specification, grades or standards.
　　A: Sales by description is the last method. Sales by description are usually applied to some whole set of electrical and l mechanical products such as equipment or instruments. For these products there must be described comprehensively for the buyers so that the buyers are able to know the structure, usage of the products, function , and so the products can be used smoothly.
　　B: In export trade, sales contract plays an important part. A major part in the contract is a quality clause, which the exporters should also pay great attention to, when working it out, so as to make it really workable.