The most important standards of quality are those belonging to the ISO9000 family. They guarantee that the manufacturer follows a standardized production system and endeavors to improve them. ISO9001 certification guarantees product conformity with the "level of quality" that the company sets. But this can also be a low level of quality. For example: Company A has been producing hand-made solid wood furniture with high quality finishing for 50 years. Company B produces poorly made furniture in chipboard which is not water-resistant, has high formaldehyde emissions and is covered with wood-patterned paper. The first is an old company whose workers know their jobs by heart and need no plans with specifications or tolerances; it doesn't even have a filing system with the plans or a standardized system of communication between its offices. The second company's production cycle is completely standardized, its offices only communicate with written messages and it has all the documentation with product designs and specifications. Even if Company A does produce excellent furniture, it still cannot obtain ISO9000 certification because its production process was never standardized according to specific procedures. Compare this to Company B which produces in paper-covered chipboard furniture, it can obtain ISO9001 certification because the production system follows all the production procedures required by ISO9001. ISO9001 standards only examine production system quality and not product quality. They guarantee that a product leaves the factory according to the specifications laid down but at any level of quality. Suppliers buying from them like these standards because they assure greater product reliability and consistency. The manufacturers like them because ISO9001 allows them to optimize their production system. They provide little or no guarantee for the final user. Certificates are issued by certification or registration bodies after inspection of the company. The system calls for repeated inspection by certification bodies.