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When a motor shaft wobbles, a skateboard wheel drags, or a 3D printer carriage binds, the culprit is almost always a worn or undersized bearing. Engineers, hobbyists, and repair technicians who work with compact rotating assemblies need a bearing that fits precisely, runs quietly, and holds up under repeated load cycles — without sourcing from a specialty distributor at inflated prices.
These miniature deep groove ball bearings feature a double metal shield (2ZZ) construction machined from bearing-grade steel. The shield keeps lubricant in and contaminants out without adding significant drag. Available sizes span the 690x series: inner diameters from 10 mm (0.39 in) to 45 mm (1.77 in), outer diameters from 22 mm (0.87 in) to 68 mm (2.68 in), and widths from 6 mm (0.24 in) to 12 mm (0.47 in). Each variant is sold in quantities of 1, 4, or 10 pieces to match your project scale.
Typical applications include RC car wheel hubs and differential assemblies, CNC router spindle supports and lead-screw end supports, 3D printer extruder idler pulleys and axis carriages, small electric motor front and rear shaft supports, and inline skate or longboard wheel axle replacements.
| Bearing Series | 690x (6900ZZ – 6909ZZ) |
|---|---|
| Shield Type | Double metal shield (2ZZ) |
| Material | Bearing steel (raceway & balls) |
| Inner Diameter (ID) | 10 mm – 45 mm (0.39 in – 1.77 in) — See variant options |
| Outer Diameter (OD) | 22 mm – 68 mm (0.87 in – 2.68 in) — See variant options |
| Width (Thickness) | 6 mm – 12 mm (0.24 in – 0.47 in) — See variant options |
| Lubrication | Pre-greased (grease retained by metal shields) |
| Bearing Type | Deep groove ball bearing |
| Pack Quantity | 1 Pcs / 4 Pcs / 10 Pcs — See variant options |
| Operating Temperature | See variant options |
| Max Speed | See variant options |
| Load Rating | See variant options |
Measure the shaft diameter (this becomes your inner diameter / ID), the housing bore (this becomes your outer diameter / OD), and the available axial space (this becomes the width). Match those three dimensions to the size listed in the variant name — for example, 6902ZZ means ID 15 mm × OD 28 mm × Width 7 mm. If you are replacing an existing bearing, the part number is usually stamped on the shield face.
"ZZ" (sometimes written as "2Z" or "2ZZ") indicates a double metal shield — one on each side of the bearing. The shields are non-contact or lightly contacting and retain the factory-applied grease while blocking coarse contaminants. They are not fully sealed like rubber-contact seals (suffix RS or 2RS), so they are best suited for clean or moderately dusty environments.
Deep groove ball bearings can accommodate moderate axial loads in addition to their primary radial load capacity. For applications where axial load is the dominant force — such as a vertical shaft with significant downward thrust — a dedicated thrust bearing is more appropriate. For mixed radial and light axial loads (typical in motors, wheels, and pulleys), these bearings perform well.
These bearings are made from bearing steel, which offers good hardness and fatigue resistance but is not inherently stainless. They are suitable for dry or lightly oiled indoor environments. For applications exposed to water, humidity, or corrosive chemicals, consider stainless steel bearings (suffix SS or AISI 440C) instead. Applying a light coat of compatible grease to the outer race before installation can help in mildly humid conditions.
Choose based on your project needs. A single piece is ideal for a one-off repair or prototype test fit. Four pieces suit a typical four-wheel RC car or a dual-shaft motor assembly with spares. Ten pieces offer the lowest per-unit cost and are practical for production batches, classroom kits, or stocking a repair drawer. All quantities ship as the same bearing — only the pack count differs.
For light-press fits, a bearing press or a correctly sized socket and mallet is recommended — always press on the ring that is being press-fitted (inner ring onto shaft, outer ring into housing) to avoid transmitting force through the balls. For hand-clearance fits, bearings can often be seated by hand or with light tapping using a plastic mallet. Avoid striking the shield face directly, as this can deform the shield and contaminate the grease.
Yes. The 690x series is widely used in 3D printer extruder idler pulleys, axis carriage linear rod supports, and CNC router spindle end supports. The 6900ZZ (10×22×6 mm) and 6901ZZ (12×24×6 mm) sizes are particularly common in compact extruder and belt-tensioner designs. Confirm the exact ID, OD, and width against your printer or machine's BOM or CAD file before ordering.
