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When a worn or corroded ball bearing causes play in a headset, bottom bracket, or wheel hub, finding the exact replacement diameter is the difference between a smooth ride and a failed repair. These 304 stainless steel loose ball bearings are stocked in 24 diameters from 6.35 mm (¼ in) to 25 mm (about 1 in), so DIY mechanics, cyclists, and workshop technicians can match the original spec without compromise.
Each ball is machined from 304 stainless steel — an austenitic alloy with a chromium content of approximately 18% — and ground to a consistent spherical tolerance. Diameters span 6.35 mm through 25 mm (roughly 0.25 in to 0.98 in), covering both metric and fractional imperial sizes including 6.35 mm (¼ in), 7.938 mm (5/16 in), 9.525 mm (3/8 in), 12.7 mm (½ in), 15.875 mm (5/8 in), 19.05 mm (¾ in). Packing options of 1, 5, or 10 pieces let you order exactly what the job requires.
Typical applications include bicycle headset and hub bearing replacement, inline skate and skateboard wheel bearings, light industrial conveyor and pivot assemblies, and marine or wet-environment mechanisms where corrosion resistance is critical. Searching for stainless steel loose ball bearings for bikes, 304 SS replacement bearing balls, or metric loose ball bearings DIY — these cover all three use cases.
| Material | 304 Stainless Steel (18/8 austenitic alloy) |
|---|---|
| Diameter Range | 6.35 mm – 25 mm (approx. ¼ in – 1 in) |
| Available Diameters | 6.35, 6.5, 7, 7.5, 7.938, 8, 9, 9.525, 10, 11, 12, 12.7, 13, 13.5, 14, 15, 15.875, 16, 17, 18, 19, 19.05, 20, 25 mm |
| Packing Quantity | See variant options (1 pcs / 5 pcs / 10 pcs) |
| Surface Finish | Precision-ground, bright |
| Corrosion Resistance | Suitable for wet and marine environments |
| Ball Type | Loose (unretained) |
| Typical Applications | Bicycle headsets, hubs, inline skates, light industrial pivots |
| Weight (per ball) | See variant options |
Remove one worn ball from the bearing race and measure its diameter with a digital caliper. Match that measurement to the closest size in the variant list. Common bicycle sizes include 3/16 in (4.76 mm — not in this range), ¼ in (6.35 mm), 5/16 in (7.938 mm), and 3/8 in (9.525 mm) for hubs, and up to ½ in (12.7 mm) for some headsets. If you are unsure, consult your component manufacturer's service documentation.
304 stainless steel has a tensile strength of approximately 515 MPa and a hardness of around 70–90 HRB. These balls are suited to light-to-medium radial loads typical of bicycle bearings, skate wheels, and small industrial pivots. For heavy-load or high-speed industrial applications requiring hardened chrome steel (52100) or ceramic balls, contact us to confirm suitability before ordering.
304 stainless steel forms a passive chromium-oxide layer that resists rust in fresh water, light salt spray, and humid conditions. It is not fully immune to pitting in prolonged exposure to concentrated chloride solutions (e.g., seawater immersion). For continuous saltwater immersion, 316 stainless steel would offer greater resistance. For most cycling, outdoor, and light marine uses, 304 performs reliably without surface treatment.
It is not recommended to mix ball materials within a single bearing race. Differences in hardness and surface finish between 304 stainless and hardened chrome steel (52100) can cause uneven wear on the race and accelerate failure. When replacing balls, replace the full complement in that bearing position with balls of the same material and diameter.
All three options contain the same 304 stainless steel balls at the selected diameter. The packing quantity determines how many balls are included per order. A single ball (1 pcs) suits a spot replacement; 5 pcs covers a typical full hub rebuild (most cup-and-cone hubs use 9–11 balls per side); 10 pcs is suited for workshop stock or rebuilding multiple bearing positions at once. Price per ball decreases with larger pack sizes.
No press tools are required. Loose balls are placed by hand directly into the bearing cup or retainer. For bicycle headsets and hubs, a thin layer of grease applied to the cup holds the balls in position during assembly. A cone wrench and lockring spanner are needed to adjust preload after installation, but the ball placement itself requires only clean hands and grease.
Older European and Japanese bicycle components typically use metric ball sizes (6, 7, 8, 10 mm, etc.), while many North American and British components use fractional imperial sizes (¼ in = 6.35 mm, 5/16 in = 7.938 mm, 3/8 in = 9.525 mm, ½ in = 12.7 mm, 5/8 in = 15.875 mm, ¾ in = 19.05 mm). Always measure the existing ball rather than relying on nominal component labelling, as tolerances can vary between manufacturers.
