This is something that you can print for kids or adults. What is really cool about it, is the fact that the plug side (because the added weight) makes the sphere always roll so the plug is down and hidden. This is a 60 mm sphere that has a very precisely made plug. The mating edge has to be perfect for it to work. Don't force the plug into the threads when you complete printing this. You may need to scrape a bit of top inside sphere hole mating edge to get the threads to properly engage (this edge will be thin so care is needed). Make sure the threads are free of debris and once you have it screwed in, work the plug in and out several times to clear the threads completely. Print with a raft and exterior support only on a slow (default) speed. Happy Printing, Makers!