Dia-Compe Brake brake caliper pivot dress up cone nut
Size: M6 (threaded diameter) X 0.8T (thread pitch) X 11mm (length)
Most every caliper brake with a acorn/cap nut on the front uses this size, but always measure to be sure. These can be used as a dress up item for the MX1000, 730, 883, etc. calipers we sell or original calipers from back in the day.