Young gemologists should be sure to keep lots of polishing grit on hand for really big rock discoveries! Our comprehensive Polishing Grit Refill Packs Set includes four different types of polishing grit: Grit #1 (Coarse); Grit #2 (Medium); Grit #3 (Fine); and Grit #4 (Polish). A perfect complement to the Rock Tumbler Pro (sold separately).