This standard stipulates the limit size of trapezoidal thread according to GB/T 5796.2-2005 "Trapezoidal Thread Diameter and Pitch Series" and GB/T 5796.4-2005 "Trapezoidal Thread Tolerance". The trapezoidal thread profile conforms to the provisions of GB/T 5796.1-2005 Trapezoidal thread profile". This standard applies to common trapezoidal threads with a nominal diameter of 8mm-300mm and a tolerance zone of 7H, 8H, 9H, 7e, 8e, 8c and 9c.