These universal mounting hubs are designed to work with most 5 mm shafts, including round shafts such as those on our stepper motors
and “D” shafts. Each hub has four mounting holes for 4-40 screws
(not included), letting you mount custom wheels or mechanisms to your
motors. 4-40 hex set screws (one included for each hub) allow secure
coupling of shaft to hub. A 0.05" hex wrench
(often the smallest size in SAE Allen wrench sets) is included for use with the set screws.