My boys love rocks! We got the hobby sized rock tumbler which comes with 4 polishing grits to polish up your rocks. We are studying geology right now and went rock hunting today. I had to order more grit to polish our new rocks. It does take a few weeks to complete the four stages of the polishing process and it is a bit loud. We will be putting it in the garage this time around. Aside from the noise, it's a great tumbler for polishing your rocks.