Despite no picture, I suspect that your crank arms have supporting shoulders for the middle ring. That means the mounting tab has to be machined in a circle to fit. Many rings are made to fit arms that don't have locating shoulders and therefore won't fit.
Tab with machined circle
wrong tabs
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Last edited by FBinNY; 08-17-14 at 11:37 AM.