This is a drop bolt for a Campagnolo brake caliper.
It allows you to use the brake caliper on a bike frame that requires a longer reach to the rim but doesn't give you rim or tire clearance for much longer arms. It also lets you convert s 27" wheeled bike to 700c wheels, since clearance issues on older steel frames tend to present themselves with the rear wheel first.
It's a smart idea. It also hasn't been manufactured in years.
That could be why this item sold on Ebay for (sit down now) $110.00.
We get requests for this part from time to time, but NO ONE is making it anymore. Here's an obvious opportunity if I ever saw one. Or is it? (Hello, Tektro? Dia-Compe? Anyone?) Discuss.