I don't know but it was my problem.I could tell a difference in the two bolts when I had them out and took the time to compare.I would try to tighten that top bolt someone had in there and it would get spongy on me before it would get real tight.So,I would stop.....I was just about to drill,tap and install a helicoil when I found this out.
Sorry I did not ask the exact specs on the bolts I bought at the store,I just bought two that matched the original bottom bolt and ran home.