Chalk holder/case - Parametric

I teach university and have to go from Classroom to classroom. The Crayola chalk they provide is awful so I got some Hagoromo chalk which writes beautifully but I didn't want loose chalk in my computer bag so I designed this parametric case to be able to always have it with me. 

I've included the .f3d file so you can customize it (you can add more spots, or more rows, change the diameter of the chalk, etc.).