Section 434 of the German Civil Code defines when goods are free of defects. Since January 1, 2022, they must meet three sets of requirements. The subjective requirements are those agreed in the contract. The objective requirements apply unless the parties have validly agreed otherwise. The goods must be fit for ordinary use and have the quality that is üblich, usual, for goods of the same kind. The third set covers assembly. Delivering the wrong item also counts as a defect. The new wording implements an EU directive. It is the legal rule behind a Reklamation, a complaint about faulty goods in a shop.
A product can match the contract and still be defective.