ISO 6149-4:2006 specifies dimensions and performance requirements for external hex and internal hex port plugs for use with ISO 6149-1 ports. Port plugs in accordance with this part of ISO 6149-4:2006 can be used at working pressures up to 63 MPa (630 bar). The permissible working pressure depends upon the plug end size, materials, design, working conditions, application, etc.