The conversion from a triple front chainring set-up to double front ring (3x to 2x conversion) can be done without buying a new crank if you select the right chainrings and accessories. These Conversion Spacer Tabs are used on the crank in place of the large ring (where it used to go). They finish the look of the crank (so it doesn't look like something is missing), and they take up the space to fit the chainring bolts for proper mounting. Check out the photos above to see how they are mounted. The first image shows just the spacers. The second shows how the spacers are mounted on the crank. Note the added red arrows. The 3rd (large) ring of a triple set usually sits in this location, but when doing the conversion, the spacer tabs take up that space to make the crank look good and for proper bolt length fit.
