These E3 tail light brackets are made in Portland, using lasers! They are cut from 5052 aluminium and then anodized. They are designed for E3 tail lights originally - the notch in the bracket allows for the wire to be moved from bike to bike or to another position without having to rewire the entire system. We've found that they are compatible with other lights or mounts that use a 50mm center to center spacing between bolt holes. Upper holes (for light mount) use M4 bolt, lower hole (for caliper brake) uses M6 sizing.
This design was made to attach at the seat stay bridge behind the brake bolt, if you were not using a rear rack.
15cm long and 6cm wide.