I just upgraded to a 56t, so my lightly used Aero 55T is now for sale. It was used at the TT's at Gila, US Pro Nationals (or half of it since I flatted), Cascade and about 500 training miles in between. $150 shipped.

Also have a Aero Q-ring 52T with about 1500 miles on it. $130 shipped

Pictures upon request.