The National Geographic Hobby Rock Tumbler Kit is a complete rock polishing kit that allows your child or teen to turn rough rocks into gemstones, making it a perfect introduction to Geology and Earth Sciences. Tumbler kit by National Geographic includes one pound of rough gemstones, eight packets of polishing grit, a storage pouch, and five jewelry fastenings. The tumbler base and motor are built to last and the tumbler barrel is designed to be low noise and leak proof. It has a built in timer and automatic shut off switch too. Now your kids can create beautiful keepsakes from your favorite specimens. Details: 11" x 12" x 2.5" (28cm x 30.4cm x 6.4cm) package size For ages 8 and up Contents: 1 tumbling machine 1 leak-proof tumbling barrel 1 bag rough gemstones (0.55 lb. / 250 g) 4 bags of polishing grits (0.7 oz. / 20 g each) 1 rock strainer 5 jewelry settings Learning guide and instructions