Pololu Universal Aluminum Mounting Hub for 6mm Shaft, M3 Holes (2-Pack)

These universal mounting hubs are designed to work with most 6 mm shafts, including round shafts and ?D? shafts. Each of the two included hubs has four mounting holes for M3 screws (not included), letting you mount custom wheels or mechanisms to your motors. The four included M3 hex set screws (two for each hub) allow secure coupling of shaft to hub, and a 1.5 mm hex wrench is included for use with the set screws.