On a Craftsman snow thrower model 536.887991 that I bought had only 2 shearpins. The ones that were on the augur. There were no extras in the case as I soon found out. I snapped a shear pin and when I checked the manual they told me about the 2 extra pins in a case on the machine. There were none there. A neighbor who had bought the same machine a month earlier loaned me one. The shear pins attached with a clip and smooth shank. When I went to the Sears store not only were they out of shear pins they were out of snowthrowers. I called the Sear 1-800 number and they sent me two quarter inch bolts fully threaded with spacers and nuts. The head of the threaded bolt is 7/16. On one side of the sleeve of the outer augur they have a hole that seems larger than the 7/16 bolt head. As a matter of fact when I put the spacer on the spacer fits inside that outer hole. When I put just the 7/16 bolt in it does not look right because 1 or 2 corners of the 7/16 head goes into the hole. I might add that when I match the head of the 7/16 bolt with the head of the original clip on shear pin the clipon shear pin has a larger head. When I went to the Sears store the parts man told me that that quarter inch, one and 3/4 length bolt with the 7/16 head is the proper part.