Pololu Universal Aluminum 3mm Mounting Hub (2-56)

* Designed to work with most 3mm shafts, including round shafts, 'D' shafts, and Tamiya's 3mm hexagonal shafts * One Allen wrench and two 4-40 set screws included * Shaft diameter: 3mm * Each hub has four mounting holes for 2-56 screws (not included) * Sold in pairs