Thank you for your visiting! *1. Mother Nature polished that stone by gently washing it in water and sand or gravel until all the rough edges were smoothed away.Then the inner colors and unique composition of the stone were uncouvered!You can do the same thing in your Rock Tumbler;it is faster than Nature，but still takes time and patience.You can expect to have beautifull，polished stones in 2 to 4 weeks.Kid can collect various kinds of rocks outdoor and whet them into extremely attractive keen diamonds with the machine.While the operation，kids can experience the fun of baor and enjoy the fulfill of success，which can devolp their curiosity and ob servations.*2. DIY toys， fun to use it.*3. No need battery， equipped with transformer.