A door or window roller cannot be selected reliably from “608ZZ,” “625ZZ” or “626ZZ” alone. The bearing code identifies the core size, while the finished pulley may add a metal housing, POM or nylon wheel, rubber or PU coating, groove and extended hub. For importers and hardware brands, separating these specifications is the first step toward fewer fitment errors and a repeatable product range.
Start with the Application, Not Only the Bearing Code
A bearing for an aluminium window roller, a wardrobe pulley, a glass sliding door or an RC model can use a similar miniature deep groove design while facing very different loads, contamination, speed and installation conditions. Before selecting a model, define the shaft, housing or finished wheel, the available space, rail and working environment.
Qingdao Gleam Hardwares reviews the bearing core and completed roller as two connected specifications. This helps a buyer avoid ordering the right bearing number inside the wrong pulley shape.
What 608ZZ, 625ZZ and 626ZZ Tell a Buyer
| Model | Common nominal bearing size* | Typical purchasing role | Information still required |
|---|---|---|---|
| 608 | 8 × 22 × 7 mm | Bearing core for many rollers, wheels and compact mechanisms | Closure, material, finished wheel OD/width, track and fit |
| 625 | 5 × 16 × 5 mm | Smaller core for compact pulley and hardware assemblies | Shaft/housing fit, closure, finished component and application |
| 626 | 6 × 19 × 6 mm | Compact bearing core used in assorted roller assemblies | Closure, pulley material, groove, installation and quantity |
*Common catalogue dimensions are shown for initial identification. Always verify the complete model, suffix, drawing and sample before ordering.
ZZ, 2RS and Other Closure Suffixes
ZZ usually indicates metal shields on both sides. RS or 2RS usually identifies a rubber seal on one or both sides. An open, shielded and sealed bearing should not be treated as automatic substitutes. Protection, friction, lubrication and operating environment must be considered together.
For a rubber-sealed option, review our 608-2RS sealed bearing for sliding door rollers. For a compact shielded core, see the 625ZZ shielded miniature bearing.
Bearing Size vs Finished Roller Size
This is one of the most important distinctions in a door-roller RFQ. A 608 bearing has a nominal 22 mm outer diameter, but an overmolded or housed roller can have a larger finished outside diameter and different total width. A search for an “8×28×10 plastic coated 608ZZ bearing” describes a completed wheel around a 608 core—not a different 608 bearing size.
| Measurement | Where to measure | Common mistake |
|---|---|---|
| Bearing bore | Inner ring or sleeve interface | Measuring the axle instead of the installed bore |
| Bearing outside diameter | Outer ring before coating or housing | Using finished wheel OD as bearing OD |
| Bearing width | Inner/outer ring width | Including an external hub or shoulder |
| Finished wheel OD | Complete rolling surface | Assuming it equals the bearing code |
| Finished wheel width | Complete roller including shoulders | Ignoring bracket clearance |
| Groove | Width, depth, radius/angle and position | Sending only a front photo without a side profile |
How to Measure an Existing Door or Window Roller
- Photograph the roller from the front, side and installed position.
- Record the complete bearing marking if readable.
- Measure the bore, finished outside diameter and total width.
- Measure the groove, shoulder and extended hub separately.
- Provide the rail section or track dimensions.
- Explain the system, environment and expected quantity.
If the old roller has a complex metal profile, compare our dual-groove metal track roller, multi-groove pulley bearing and flanged extended-hub roller assemblies. For compact equipment and RC applications, see our miniature deep groove ball bearing range.
Shielded Bearing, Sealed Bearing or Finished Coated Wheel?
| Product form | What the buyer receives | Best RFQ starting point |
|---|---|---|
| Bare shielded bearing | Bearing core with metal shields | Full code, dimensions, fit, lubrication and quantity |
| Bare sealed bearing | Bearing core with rubber seal arrangement | Full suffix, environment and friction/protection requirements |
| Plastic-coated bearing wheel | Bearing plus POM/nylon or another polymer profile | Finished OD, width, material, groove, colour and track |
| Metal pulley bearing | Bearing integrated with a formed or machined rolling profile | Section drawing, hub/flange, rail and approved sample |
| Custom roller assembly | Bearing, wheel/housing and installation features | Assembly drawing, mating parts and application test |
Our existing plastic bearing roller wheel family covers POM, nylon and related finished-wheel enquiries. The new pages focus on bearing cores and metal roller geometries so each page answers a different procurement question.
Quality Evidence for Sample Approval
A meaningful sample review compares the item with the buyer’s drawing or approved reference. Useful checks include the full model marking, bore, outside diameter, width, closure appearance, rotation, roller profile, hub dimensions and assembly fit. For a finished wheel, groove contact and concentricity should be checked using an agreed method.
Claims such as “high speed,” “heavy duty” or “long life” are not acceptance criteria by themselves. If those properties matter, include the operating conditions, test method and acceptable result in the specification.
RFQ Checklist for Importers
| RFQ field | Useful information |
|---|---|
| Bearing code | 608ZZ, 608-2RS, 625ZZ, 626ZZ or full alternative code |
| Verified dimensions | Bore × bearing OD × bearing width; finished wheel OD × width |
| Roller profile | Flat, U-groove, V-groove, multi-groove, flange or extended hub |
| Material | Bearing grade and any POM, nylon, rubber, PU or metal outer profile |
| Application | Door/window type, rail, bracket and working environment |
| Commercial requirement | Estimated quantity, target market, label and packaging |
| Reference | 2D drawing, sample, track section or measured photographs |
Frequently Asked Questions
Are 608ZZ, 625ZZ and 626ZZ interchangeable?
No. They have different nominal dimensions. The shaft, housing and finished roller must be checked.
Is 608ZZ the same size as 608-2RS?
The basic 608 boundary dimensions are commonly the same, but the closure and operating behaviour differ. Confirm the complete suffix and application.
Can a finished pulley be quoted from the bearing code only?
No. Provide finished outside diameter, width, groove, hub or flange, material, rail and quantity.
Can a discontinued roller be reproduced from a sample?
It can be evaluated. A physical sample plus the mating rail or bracket gives a stronger basis than photos alone.
Which details reduce repeat-order mistakes?
A controlled drawing, approved sample, full model and suffix, label format, carton quantity and inspection record create a clearer repeat-order standard.
Need Help Matching a Bearing Core and Finished Roller?
Send the bearing code, verified dimensions, drawing or application photos, expected quantity and destination market. Qingdao Gleam Hardwares will review the technical and packaging requirements for an OEM quotation.
