Pulley, Timing, Spindle, HiTorque Mini Mill
Weight: 0.41 lb
This is a timing belt pulley for type 5M belts.
It has 40 cogs. The bore is 28 mm in diameter and has a 6 mm keyway. The total length of the pulley and hub is 37 mm.
In your instruction manual, this part appears on the parts list as: