My contempt for the decay of National Geographic as a standard bearer of quality and integrity and beautiful purposeful design was cemented with this rock polishing kit. Everything about it was substandard. The initial supplies are pitiful. The rock samples provided are uninspiring. The sand samples are good for one small pass and then your kid is off to the craft store hoping to find more. Sooo much cheap plastic. The electricity bill will ruin you as it runs for hours + days just for a wee batch. And the design mechanics are a nightmare. After a run tumbles the plastic halves would jam up binding together like superglue. I had four grown men attempt to open it on the last use!!! Now imagine a 10-year-old girl trying to pry it apart. Highly do not recommend. 0 rating if I could. Bad everything including advertising deception. My daughter hasn't touched a rock since! National Geographic now specializing in sucking the truth and passion out of everything.