Ultra-Long Spin SR188UU Center-Trac U-Groove Stainless Bearings for Competition Yoyos
| Item No : | SR188UU / R188UU / SR188-KK |
| Size (d*D*B) : | 6.35 x 12.7 x 4.762 mm |
| Material : | AISI 420 Martensitic Stainless Steel |
| Lead Time : | 3-5 days |
| Weight : | 0.002KG |
| MOQ : | 100 pcs |
⚙️Bearing Description:
The SR188UU (6.35 x 12.7 x 4.762 mm / 1/4″ x 1/2″ x 3/16″, Size C) is an open-type inch miniature deep groove ball bearing specially engineered with an integral U-groove (concave / KK profile) on the outer race ring for high-performance Yoyos and precision fidget spinners. Crafted from premium AISI 420 martensitic stainless steel, its curved outer channel automatically centers the string away from the response pads, drastically reducing string friction during complex trick combinations. Featuring mirror-polished raceways and high-precision stainless steel balls with a ultra-light dry lube or unshielded open design, it ensures maximum sleep times, ultra-low rotational resistance, and instant acceleration. We supply these specialty concave yoyo bearings under our proprietary RMO brand while offering flexible multi-brand OEM direct sourcing for competitive yoyo manufacturers and EDC spinner brands globally.
⚙️Bearing Features:
- Integral String-Centering U-Groove (KK Profile): Concave outer ring design automatically aligns the string in the dead center, eliminating pad friction for extended spin time.
- Corrosion-Resistant AISI 420 Stainless Steel: Martensitic stainless steel rings and balls resist hand sweat, ambient humidity, and oxidation without rusting.
- Unshielded Open Architecture for Max Speed: Open structure without dust shields minimizes rotational drag and allows easy dry-cleaning and high-spin lubrication.
- High-Precision Micro-Honed Raceways: ABEC-3/ABEC-5 tolerance grade raceways ensure high dynamic balance, zero wobble, and whisper-quiet rotation during intense trick combos.
⚙️Bearing Applications:
Engineered for string centering, ultra-low rolling drag, and extended free-spinning times, the SR188UU U-groove bearing is widely specified in:
- Competitive yoyos (1A, 3A, 5A styles): metal unresponsive yoyos, bi-metal trick yoyos, and plastic-metal hybrid competition yo-yos.
- EDC fidget spinners & novelty toys: high-end titanium/copper fidget spinners, desktop spin tops, and kinetic desk toys.
- Precision micro-mechanisms: specialized cable/filament guide pulleys, micro tensioning rollers, and low-friction optical instruments.
⚙️Precautions:
| 1. Keep clean | 2. Use with caution | 3. appropriate tool | 4. Hot-loading | 5. Be careful of rust |
| Dust will have a bad effect on the bearing, so keep the surrounding clean. | Strong impact during use can easily cause scratches and indentations. | Avoid replacing existing tools, and use appropriate tools. | Bearings are precision parts, so hot installation is recommended. | Sweat on your hands during operation will cause rust, so it is best to wear gloves. |
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⚙️Obtain Certificate:
About Rimao
Since its establishment in 2011, Rimao Bearing has combined international vision with local wisdom and injected innovative ideas into every bearing and pulley with its profound industry accumulation and unremitting pursuit of technology. We have not only passed CE and ROHS certification, but also set a new benchmark in the industry and led the development trend of the bearing industry.
We are not just a ball bearing and roller bearing importer and wholesaler. We provide real solutions to help you achieve the product and design goals set by your customers. With more than 20 years of production and sales experience, tens of thousands of models and specifications, we look forward to cooperating with you!
⚙️Technical Parameters:
| Model No. | SR188UU / R188UU / SR188-KK |
| Bearing Type | U-Groove Yoyo Bearing |
| Standard Size Code | Size C Yoyo Bearing (1/4″ x 1/2″ x 3/16″) |
| Key Dimensions | 6.35×12.7×4.762mm (Inner d x Outer Dia D x Total Width/Height H) |
| Key Dimensions (In) | Bore=0.250 in, OD=0.500 in, Width=0.1875 in |
| Outer Ring Profile | U-Groove / Concave Center-Trac Profile |
| Material | AISI 420 Martensitic Stainless Steel |
| Shield Type | Open / Unshielded Open Design |
| Cage Material | AISI 304 Stainless Steel / Steel Retainer |
| Precision Rating | P6(ABEC‑3) / P5(ABEC‑5) Optional |
| Target Application | Competition Yoyos, Fidget Spinners, Filament Guides |
| Brand | RMO (Own Brand) / Neutral / OEM Custom / Other Global Brands |
| Packing Method | |
| Lead Time | 3-5 days for stock; 7-15 days for bulk orders |
| Shipping Port | Guangzhou, Ningbo, Shanghai |
| Payment | 100% T/T, or 30% T/T In Advance, 70% T/T After Finished Production |
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