Originally Posted by
Andrew R Stewart
The serrations in the ring bolt hole are artifacts from a female half of the ring bolt and nut which had serrations in it's outer surface to better grip the ring hole. More common on cranks that have the 5th hole positioned behind the crank arm, as it's hard to get a ring nut wrench in there.
The plastic bit looks a lot like a plug for some hole. At about 4mm in diameter (for the "shaft") I suspect it's meant to fit in a M% threaded hole. maybe a bottle cage boss. Anyway I doubt it's intended to be used on the ring, likely just was along for the ride in the packaging. Andy.
Ok - you are exactly right about the serrations in the bolt eye. From what I can find, my chainring has a nut pressed into the bolt eye because one of the bolt is hidden by the arm. Apparently it is common to Sram 22 speed systems. I had no noticed one bolt eye is hidden until now. I guess Sram tried to make it look like Shimano and FSA 4 bolt system.
The seller just buys stuff from sales like garage sales and then sells on auction site. She does not know the origin of the plastic plug.