# Best rock tumbler replacement belts and how to pick the size Source: https://tumblegrit.com/best/best-rock-tumbler-belts Publisher: Tumble Grit. Picks are chosen from what each Amazon listing states, not from hands-on tests. Method: https://tumblegrit.com/how-we-pick When the barrel stops turning, a slipped, stretched or broken belt is the first thing to check, ahead of an overloaded barrel or wet rollers. The fix is a small round drive belt, but belts are not universal: each tumbler family uses its own length and thickness, and a belt of the wrong size will slip or not go on at all. So pick by model first: find the model name on your machine and buy a pack whose listing names it. You must match the belt to your tumbler; nothing below is a universal part. If your model is not named anywhere, measure the old belt and compare it with a listing that gives dimensions; only two of the packs here state a size. After fit, the packs differ in material (plain rubber, nitrile rubber, which is also sold as Buna-N, or polyurethane) and in how many belts you get, from 4 to 12. A belt is a wear part, so spares are worth having. This guide compares what each listing states about fit, pack count, material and size. Nothing here was tested, and no compatibility is assumed beyond what a listing names. ## Picks ### 1. RTumbler Brand Replacement Drive Belt 5 Pack Compatible with Lortone 33B, 3-1.5, 45C Tumblers Fits: Lortone 33B, 3-1.5, 45C; Pack: 5 belts; Material: Buna nitrile; Size: not stated Five O-ring style Buna nitrile belts compatible with the Lortone 33B, 3-1.5 and 45C. The listing gives a 15 year shelf life, so the spares can wait in a drawer. What the listing offers: - Title names three Lortone models: 33B, 3-1.5 and 45C. - O-ring style belts made from Buna nitrile, described as more flexible and abrasion resistant than natural rubber. - Listing states a 15 year shelf life and that the belts stay pliable down to -20 F. Limits to know: - Not an original Lortone part: the title calls it a replacement belt compatible with those models. - No belt dimensions are given, and the Lortone 3A is not covered by this pack. ### 2. 4 Pack Round Drive Belts for LORTONE 3A KomeStone K1 K3 Fits: Lortone 3A, KomeStone K1, K3; Pack: 4 belts; Material: Buna-N nitrile; Size: not stated Four round Buna-N belts for the Lortone Model 3A and the KomeStone K1 and K3. The listing says plainly that they do not fit the K2 or K4. What the listing offers: - Specifically designed to fit the Lortone Model 3A and KomeStone K1 and K3 rock tumblers. - States what it does not fit as well: not applicable to the KomeStone K2 or K4. - Four identical belts made from Buna-N (nitrile) rubber to resist abrasion and stretching. Limits to know: - Four belts is the smallest pack count in this guide, shared with the National Geographic set. - No length or thickness is given, and the KomeStone K1 Pro is not named in this listing. ### 3. Upgraded Rock Tumbler Drive Belts Fits National Geographic and Dr. Cool Fits: Nat Geo, Dr. Cool tumblers; Pack: 4 belts; Material: Polyurethane; Size: not stated Four O-ring style polyurethane belts for National Geographic hobby and professional series tumblers and Dr. Cool tumblers. The pack to look at for the common kit machines. What the listing offers: - Listing names National Geographic hobby and professional series tumblers plus Dr. Cool brand tumblers. - Made from polyurethane, which the listing says resists stretching and wear. - Four identical O-ring style belts in the pack, matching the original belt configuration. Limits to know: - No belt length or thickness is given, so you cannot check it against the old belt before ordering. - Says it fits 'various barrel sizes' without listing exact model numbers, and the brand is little known. ### 4. 5pcs Replacement Drive Belt for Harbor Freight Chicago Electric Rock Tumblers - Fits ABN, Viyuki, Central Machinery - Durable Nitrile Rubber for Dual & Single Barrel Models Fits: Harbor Freight, ABN, Viyuki; Pack: 5 belts; Material: Nitrile rubber; Size: not stated Five round nitrile rubber drive belts for Harbor Freight Chicago Electric single and dual barrel tumblers, also listed for Central Machinery, ABN and Viyuki machines. What the listing offers: - Designed for Harbor Freight Chicago Electric single and dual barrel rock tumblers. - Listing also names Central Machinery, ABN and Viyuki tumblers as compatible. - Abrasion-resistant, oil-proof nitrile rubber in a round belt design, five to a pack. Limits to know: - No dimensions are stated, and exact model numbers for the ABN and Viyuki machines are not given. - Sold under an unfamiliar brand name with no warranty term in the listing. ### 5. KEEPOW 5 Pack Rock Tumbler Belts, Replacement Belt Set Fits: K1/K3, C1/C3, Thumler's A-R; Pack: 5 belts; Material: Rubber; Size: 9.56 in loop, 0.15 in wide Five rubber belts with the broadest fit list here: KomeStone K1, K1 Pro and K3, KoolStone C1, C1 Pro and C3, and Thumler's A-R series. One of two packs that state the belt size. What the listing offers: - Lists KomeStone K1, K1 Pro and K3, KoolStone C1, C1 Pro and C3, and Thumler's A-R1, A-R2, A-R3, A-R6, A-R12 and B#401. - Gives the size: 24.3 cm (9.56 in) perimeter, 0.4 cm (0.15 in) wide, 7.8 cm (3.04 in) diameter. - Carries a note that it is not compatible with the KomeStone K2 Elite, which helps avoid a wrong order. Limits to know: - Plain rubber, where several other packs here use nitrile rubber or polyurethane. - One size is claimed for three brands; measure your old belt against the stated 9.56 in before ordering. ### 6. 10 Pcs Rock Tumbler Drive Belt Compatible with Thumler's A-R1, A-R2, A-R3, A-R6, A-R12 and Model B Tumblers, Nitrile Rubber Belt for Thumler's A-R1 Fits: Thumler's A-R and Model B; Pack: 10 belts; Material: Nitrile rubber; Size: not stated Ten nitrile rubber belts for Thumler's A-R1, A-R2, A-R3, A-R6, A-R12 and Model B tumblers, with a textured anti-slip surface instead of a smooth one. What the listing offers: - Listing names Thumler's A-R1, A-R2, A-R3, A-R6, A-R12 and Model B rotary tumblers. - Nitrile rubber (Buna-N) that the listing rates for temperatures from -20 F to 250 F. - Ten belts per pack, with an anti-slip textured surface meant to improve grip on the pulley. Limits to know: - The claim of 30 percent better torque transfer is the seller's own figure with nothing in the listing to back it. - No belt dimensions are stated, and one size for both the small A-R models and the Model B deserves a check against your old belt. ### 7. Leegol Electric Rock Tumbler Replacement Drive Belt 12 Pack Belt Size: Dia 32 x 5 mm Fits: Leegol blue tumblers; Pack: 12 belts; Material: not stated; Size: Dia 32 x 5 mm The largest pack here: twelve drive belts, sized Dia 32 x 5 mm in the title, listed as non-OEM replacements for Leegol Electric blue tumblers. What the listing offers: - Twelve belts in one pack, the most of any listing in this guide. - Title states the belt size as Dia 32 x 5 mm, so you can compare it with the belt you are replacing. - Described as having greater flexibility and abrasion resistance than natural rubber, with a manufacturer warranty. Limits to know: - Fit is given only as 'Leegol Electric blue tumblers'; no model numbers are named. - The material is not named, and the listing calls these non-OEM belts. ### 8. AtoRock Rock Tumbler Replacement Belts, Compatible A1&A1 Pro Rock Tumbler, 5Packs Fits: AtoRock A1, A1 Pro; Pack: 5 belts; Material: not stated; Size: not stated Five replacement belts sold by AtoRock for its own A1 and A1 Pro tumblers. The listing is a single line, so fit and count are all it tells you. What the listing offers: - Sold under the AtoRock name for the AtoRock A1 and A1 Pro rock tumblers. - Five belts in the pack, enough spares for several replacements. - Fit is limited to two named models rather than a long list of loosely related machines. Limits to know: - The listing does not state the belt material, length or thickness. - Only one line of description, with nothing on other AtoRock models or other brands. As an Amazon Associate I earn from qualifying purchases.