Look for the tag on the product which will have the size and other product information mainly inside the shoe that is behind the tongue of the shoe. Real Adidas shoes have tags with serial numbers for the left and right shoe. However, a fake product will have the same serial number on both shoes.

Adidas Originals (often stylized as adidas Originals) is a brand of a line of casual and sportswear created by German multinational corporation Adidas. It consists of a heritage line, specializing in athletic shoes, t-shirts, jackets, bags, sunglasses and other accessories.

The tags have the size and product information on the inside of the shoe (behind the tongue).

Adidas AG (German pronunciation: [ˈʔadiˌdas]; stylized in all lowercase since 1949) is a German athletic apparel and footwear corporation headquartered in Herzogenaurach, Bavaria, Germany.