All rings are placed into slots in the base, and glued if necassary. Once assembled, the balls will not fall out of the puzzle, even when upside-down. The design at 100% uses 3/8" ball bearings. (https://www.amazon.com/gp/product/B007B2AG7W/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1)
The author marked this model as their own original creation.