Transportable pressure vessels for high-pressure gases are routinely inspected and tested as part of the manufacturing process. They are generally marked as evidence of passing the tests, either individually or as part of a batch (some tests are destructive), and certified as meeting the standard of manufacture by the authorised testing agency, making them legal for import and sale. When a cylinder is manufactured, its specification, including manufacturer, working pressure, test pressure, date of manufacture, capacity and weight are stamped on the cylinder.