This object was made of white jade, with brown, yellow and black stains left by permeation on its surface. It has raised edge around the hole on both sides, and four bulges each with five teeth on its edge.The bulged bi disk is a special form of Bi disks, usually having three or four bulges with some tooth. Collared Bi Disks are both unearthed in Jinsha and Sanxingdui sites, and mostly they are exquisite. Therefore, they might be a sort of popular type of jade object in Sichuan in Shang and Zhou Dynasties. Prior to the Jinsha discovery no four bulged bi disk had been found in somewhere else. Particularly, this object is large in size and heavy in weight; archaeologists assume that it should be a self-creation by the ancient Jinsha people with distinctive Jinsha feature.