IBM Selectric Type Element Tray Modifications

This is a modification to the IBM Selectric Type Element Tray by Twylo on Thingiverse: https://www.thingiverse.com/thing:3891684

I added posts to the centers of the holes to allow the balls to clip onto them so they won't turn or fall out. I also created larger trays with 18 and 36 ball holders.