Flange bolts are identifiable by a ridge below the bolt head. This built-in washer distributes the clamping load over a greater area. Commonly used by assembly line workers in the automotive industry,Website:http://www.chinajinrui.net, these bolts are designed to provide the same holding power as a washer.A Flange Bolt is a method of connecting pipes, valves, pumps and other equipment to form apipework system.Flange bolts are usually screwed into such systems.GB national standard is one kind of standard of our country, in addition to industry standards, and professional standards. The national standard is divided into: GB (mandatory standards) and GB/T (recommended standard) and GBn (standard internal state).