Chainrings wear from chain contact under pedaling loads, and when the teeth start showing hooked profiles or the chain no longer sits flush on the ring, shifting degrades and you risk dropping chains. This thirty-nine-tooth inner ring replaces worn rings on Campagnolo Record and Chorus cranksets that use the one hundred thirty-five millimeter bolt circle diameter with five-bolt mounting. The ring works with eight-speed, nine-speed, and ten-speed drivetrains, though it was designed during the ten-speed era when Campagnolo used this particular BCD and bolt pattern.

Campagnolo machines this ring from seven thousand seventy-five aluminum billet, which is an aerospace-grade alloy that handles the cyclic stress of pedaling while keeping weight down compared to standard aluminum grades. The AFT finish refers to Anti-Friction Treatment, which creates a matte gray surface that reduces friction between the chain and ring during shifts. The treatment also provides some corrosion resistance compared to untreated aluminum, though you should still clean the ring regularly since chain lube attracts grit that accelerates wear.

The ring mounts with five chainring bolts arranged in a one hundred thirty-five millimeter circle. This BCD was common on Campagnolo cranksets before they moved to the one hundred twelve millimeter standard for their eleven-speed and newer groups. If you have a Record or Chorus crankset from the eight-speed through ten-speed generations, you can identify the correct BCD by measuring from the center of one bolt hole to the center of an adjacent bolt hole and multiplying by one point seven. You need the original five chainring bolts to mount this ring, which are sold separately.