Gear guide
Best grit refills for a National Geographic rock tumbler
Picked from Amazon listings, not hands-on tests. How we pick
A National Geographic kit tumbler comes with grit packets, one per step, and once they are used up the owner needs a refill. The choice is between the branded grit refill, a branded bundle that adds rough rocks, and a generic 4-step kit. The steps are the same in every case: step 1 is coarse grit (60/90 silicon carbide in most generic kits), step 2 is medium grit (150/220), step 3 is fine or pre-polish grit (500 or 600) and step 4 is polish, usually aluminum oxide. What differs is the format (packets, small bags or bulk containers), how much rock the seller says the pack covers, and what else is in the box: ceramic media, polishing foam, rough rocks or jewelry settings. For packet kits, follow the tumbler manual for amounts; longer runs in step 1 give better shape. This guide compares seven refills that carry the brand or name these tumblers in the listing, using only what the listings state. Tumble Grit is independent and is not affiliated with National Geographic.
Compare the picks
| Pick | Fit stated | Grit format | Coverage stated | Also in the box | Price | Link |
|---|---|---|---|---|---|---|
 National Geographic grit and media refill kit | Branded refill | Bulk, screw-top containers | 8 to 10 lb of rocks | 1.5 lb ceramic, GemFoam | - | Amazon |
 AtoRock 4-step grit kit with dual media, 10 lb | Title names the brand | Bulk, 7 lb of grit | Up to 70 lb of rocks | 2 lb ceramic, 1 lb pellets | - | Amazon |
 National Geographic refill kit with 5 lb rough rocks | Branded refill | 20 packets | 5 tumbling cycles | 5 lb rocks, 5 settings | - | Amazon |
 National Geographic grit, media and 3 lb rocks kit | Branded refill | Screw-top containers | 8 to 10 lb of rocks | 3 lb rocks, ceramic, GemFoam | - | Amazon |
 KoolStone 4-step grit refill, four 1 oz bags | Title names the brand | 4 bags, 1 oz each | not stated | Nothing else stated | - | Amazon |
 National Geographic grit and polish refill kit | Branded refill | 4 screw-top containers | Up to 20 lb of rocks | Nothing else stated | - | Amazon |
 National Geographic refill kit, 1 lb gemstone mix | Branded refill | not stated | not stated | 1 lb rocks, fastenings | - | Amazon |
Facts are taken from each Amazon listing. Prices are checked daily and shown with their date.
If you just want one
- Closest match for the jobNational Geographic grit and media refill kitIncludes 1.5 lb of ceramic pellets, described as filler for smaller batches that also quiets the tumbler and reduces breakage.
- Most for the money on paperKoolStone 4-step grit refill, four 1 oz bagsPortioned much like the packets of a kit tumbler: one 1 oz bag per step, four bags in total.
- Most complete listingAtoRock 4-step grit kit with dual media, 10 lbGrades and weights are stated for all four steps, which the branded refill listings do not give.
The picks in detail
Pick 1 · Blue Marble
National Geographic grit and media refill kit
See price on AmazonA branded refill that pairs 4-stage bulk silicon carbide grit with 1.5 lb of ceramic pellets and GemFoam polishing media. The listing says the grit polishes 8 to 10 lb of rocks and that a measuring scoop is included.
What the listing offers
- Includes 1.5 lb of ceramic pellets, described as filler for smaller batches that also quiets the tumbler and reduces breakage.
- A measuring scoop and storage containers with screw-top closures come with the grit.
- GemFoam polishing media is included, to be added to the tumbler after the final grit cycle.
Limits to know
- Stated coverage is 8 to 10 lb of rocks, less than the 20 lb quoted for the grit-only branded refill.
- Weights and grades of the individual grit stages are not stated in the listing.
Pick 2 · AtoRock
AtoRock 4-step grit kit with dual media, 10 lb
See price on AmazonA bulk generic kit whose title calls it ideal for National Geographic tumblers: 2 lb of 60-grit coarse, 2 lb of 150-grit medium and 1.5 lb of 600-grit fine silicon carbide, 1.5 lb of 1200-grit aluminum oxide, plus ceramic media and plastic pellets.
What the listing offers
- Grades and weights are stated for all four steps, which the branded refill listings do not give.
- Includes 2 lb of ceramic tumbler media and 1 lb of plastic pellets alongside the grit.
- The listing gives a dose of 2 scoops of grit per 1 lb of stones and 7 to 10 days of rolling time per stage.
Limits to know
- Ten pounds is a large supply for a 1 lb or 2 lb kit tumbler, and 3 lb of it is media rather than grit.
- Bulk grit has to be measured for every step; nothing is pre-portioned like the packets of a kit tumbler.
Pick 3 · Blue Marble
National Geographic refill kit with 5 lb rough rocks
See price on AmazonThe packet-style refill: 20 grit packets, which the listing says is enough for five complete tumbling cycles, with 5 lb of rough rocks in four mixes. It keeps the packet-per-step routine of the kit tumbler.
What the listing offers
- 20 grit packets, stated as enough for five complete tumbling cycles with any rock tumbler.
- 5 lb of rough rocks: 2 lb of gemstone mix and 1 lb each of agate mix, Madagascar mix and jasper mix.
- Five jewelry settings, a storage pouch and a learning guide with polishing instructions are included.
Limits to know
- Packet weights and grit grades are not stated, so the grit per cycle cannot be compared with bulk kits.
- Much of the pack is rocks and jewelry settings; an owner who only needs grit is buying extras.
Pick 4 · Blue Marble
National Geographic grit, media and 3 lb rocks kit
See price on AmazonA full restock in one box: grit the listing says polishes 8 to 10 lb of rocks, 3 lb of rough rocks from Madagascar, ceramic tumbler media and GemFoam. It suits an owner who has run out of both grit and rough.
What the listing offers
- Comes with 3 lb of rocks from Madagascar; the listing says the pack can include rose quartz, jasper and other varieties.
- Ceramic tumbler media and GemFoam polishing media are both included alongside the grit.
- A measuring scoop and storage containers with screw-top closures are part of the pack.
Limits to know
- The rock mix is not fixed: the listing says it can include certain varieties, so the exact stones are not known in advance.
- The weight of the ceramic media and of each grit stage is not stated in this listing.
Pick 5 · KoolStone
KoolStone 4-step grit refill, four 1 oz bags
See price on AmazonA generic small refill: one 1 oz bag each of step 1 coarse grit, step 2 medium grit, step 3 pre-polish and step 4 final polish. The title lists National Geographic among the compatible tumbler brands.
What the listing offers
- Portioned much like the packets of a kit tumbler: one 1 oz bag per step, four bags in total.
- The title names National Geographic, Komestone and Koolstone tumblers as compatible.
- The listing states the weight of every bag, so the amount per step is known before buying.
Limits to know
- Only 4 oz of grit in total, with no spare coarse grit if step 1 has to be repeated.
- Grit grades and materials are not given by number or name, only as coarse, medium, pre-polish and final polish.
Pick 6 · Blue Marble
National Geographic grit and polish refill kit
See price on AmazonThe branded 4-step refill sold for the National Geographic kit tumblers. The listing says the silicon carbide grit polishes up to 20 lb of rocks and works with all rock tumblers; weights and grades are not given.
What the listing offers
- Four stages in one pack: initial shaping, smoothing, pre-polish and final polish, each in its own container.
- Each stage is packaged in a wide-mouth container with a screw-top closure for measuring and storage.
- Stated to work with all rock tumblers and to cover up to 20 lb of rocks, gems, glass and more.
Limits to know
- The listing does not state the weight of the kit or of any step, so it cannot be compared pound for pound.
- Grit grades and the polish type are not given, and no media, scoop or instructions are mentioned.
Pick 7 · Blue Marble
National Geographic refill kit, 1 lb gemstone mix
See price on AmazonA small branded restock: 1 lb of gemstone mix with four grades of grit (coarse, medium, fine, polish), jewelry fastenings and a learning guide. Sized as a small top-up rather than a bulk supply.
What the listing offers
- Four grades of grit are included: coarse, medium, fine and polish, matching the four steps.
- Comes with 1 lb of gemstone mix, so rough rocks and grit arrive together.
- Jewelry fastenings (necklace, earrings, keychain, ring) and a learning guide are in the kit.
Limits to know
- The listing does not say how much grit is included or how many loads it covers.
- The stones in the gemstone mix are not named, and grit grades are not given by number.
Read before you buy
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Tumble Grit chooses every product independently from what its Amazon listing states. We may earn a commission from the links above. As an Amazon Associate I earn from qualifying purchases.