Dia-Compe brake lever clamp bolt, washer, and nut.
DIA COMPE Tech 3 Brake Lever Clamp Bolt
Size: M5 (threaded diameter) X 0.8 (thread pitch) X 20mm (length)
The special low profile, lightweight, recessed nut is made of aluminum.
These fit the following Dia-Compe lever models: Tech 2, Tech 3, Tech 4, Tech 6