ISO 6149-2:2006 specifies dimensions, performance requirements and test procedures for metric adjustable and non-adjustable heavy-duty (S series) stud ends and O-rings.Stud ends in accordance with ISO 6149-2:2006 may be used at working pressures up to 63 MPa (630 bar) for non-adjustable stud ends and 40 MPa (400 bar) for adjustable stud ends. The permissible working pressure depends upon the stud end size, materials, design, working conditions, application, etc.