Cog for IKEA blind

This is a cog for a project involving being able to pull up a blind from IKEA. They use a string with spheres on it for pulling the blind up and down. This cog fits the spheres perfectly and is made to fit the rod of a stepper motor. The blind I am designing for is linked below.

http://www.ikea.com/us/en/catalog/products/10309150/

** Update **
I have now changed so that the center hole is straight through instead of stopping 2 mm from one side.