Indispensable screws, and create a better future of the world - Heng Xin Jie. Non-standard cylindrical pin, hex bolt tail, Xin Heng Jie screw manufacturers. GB- national standard is one of the many standards, in addition to industry standards, professional standards and departmental standards. National standard is divided: GB (mandatory standards) and GB / T (recommended standards) and GBn (national internal standard). We normally see as GB30, GB5783, etc. are mandatory standards.