These handlebar brackets fit 3-rail, 5-rail, and 7-rail CETMA Racks, and are compatible with most newer bikes with upright bars. Hardware included.
Note: These brackets can be found at hardware stores. Commonly known as "conduit hangers", they're used by electricians to attach electrical conduit to walls. While they're not specifically made for bicycles, their size, design, and obtainability make them perfect. I'm telling you this so that you won't feel dumb when your electrician-neighbor says, "Hey man, those are conduit hangers".