This is a 32 tooth middle 4 hole Titanium ring. It fits all modern 4 arm Shimano compact chainsets. That means the nice new Hollowtech ones, both Octalink and standard axle.	The rings have four pins and special tooth profiles which assist the chain in it's climb from the granny ring under power. Back to Titanium Chainrings Review
This ring will out last an aluminium one by four times.