Independent technical reference

Small ball bearing reference: metric, inch, open, ZZ and 2RS sizes

Use the complete catalogue designation to compare dimensions. A base model, its shielded version and its sealed version may have different widths. This reference keeps metric and inch source units, publisher identity and recorded closure separate, with real 1600-series, R-series and miniature metric examples.

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Catalogue variant evidence

Find the full model, closure and actual width

Compare named records from the SMB metric/imperial ball-bearing charts and Enduro 1600-series table. The source unit is retained beside the converted unit. A shield or seal can change the width; equal bore and outside diameter do not establish the same envelope.

728 source-labelled records; 24 shown initially.

Publisher / full model	Closure / material	d×D×B in mm	d×D×B in inches	Source unit
SMBR133	OpenChrome steel	2.37998×4.7625×1.5875 mm	0.0937×0.1875×0.0625 in	inch
SMBR133ZZ	ShieldedChrome steel	2.37998×4.7625×2.37998 mm	0.0937×0.1875×0.0937 in	inch
SMBR144	OpenChrome steel	3.175×6.35×2.37998 mm	0.125×0.25×0.0937 in	inch
SMBR144ZZ	ShieldedChrome steel	3.175×6.35×2.77876 mm	0.125×0.25×0.1094 in	inch
SMBR2-5	OpenChrome steel	3.175×7.9375×2.77876 mm	0.125×0.3125×0.1094 in	inch
SMBR2-5ZZ	ShieldedChrome steel	3.175×7.9375×3.57124 mm	0.125×0.3125×0.1406 in	inch
SMBR2-6	OpenChrome steel	3.175×9.525×2.77876 mm	0.125×0.375×0.1094 in	inch
SMBR2-6ZZ	ShieldedChrome steel	3.175×9.525×3.57124 mm	0.125×0.375×0.1406 in	inch
SMBR2	OpenChrome steel	3.175×9.525×3.96748 mm	0.125×0.375×0.1562 in	inch
SMBR2ZZ	ShieldedChrome steel	3.175×9.525×3.96748 mm	0.125×0.375×0.1562 in	inch
SMBR2-2RS	SealedChrome steel	3.175×9.525×3.96748 mm	0.125×0.375×0.1562 in	inch
SMBR2A	OpenChrome steel	3.175×12.7×4.36626 mm	0.125×0.5×0.1719 in	inch
SMBR2AZZ	ShieldedChrome steel	3.175×12.7×4.36626 mm	0.125×0.5×0.1719 in	inch
SMBR2A-2RS	SealedChrome steel	3.175×12.7×4.36626 mm	0.125×0.5×0.1719 in	inch
SMBR155	OpenChrome steel	3.96748×7.9375×2.77876 mm	0.1562×0.3125×0.1094 in	inch
SMBR155ZZ	ShieldedChrome steel	3.96748×7.9375×3.175 mm	0.1562×0.3125×0.125 in	inch
SMBR156	OpenChrome steel	4.7625×7.9375×2.77876 mm	0.1875×0.3125×0.1094 in	inch
SMBR156ZZ	ShieldedChrome steel	4.7625×7.9375×3.175 mm	0.1875×0.3125×0.125 in	inch
SMBR156-2RS	SealedChrome steel	4.7625×7.9375×3.175 mm	0.1875×0.3125×0.125 in	inch
SMBR166	OpenChrome steel	4.7625×9.525×3.175 mm	0.1875×0.375×0.125 in	inch
SMBR166ZZ	ShieldedChrome steel	4.7625×9.525×3.175 mm	0.1875×0.375×0.125 in	inch
SMBR166-2RS	SealedChrome steel	4.7625×9.525×3.175 mm	0.1875×0.375×0.125 in	inch
SMBR3	OpenChrome steel	4.7625×12.7×3.96748 mm	0.1875×0.5×0.1562 in	inch
SMBR3ZZ	ShieldedChrome steel	4.7625×12.7×4.9784 mm	0.1875×0.5×0.196 in	inch

Page 1

Separate Enduro series ratings — do not transfer them to SMB variants

The original series table supplies these N and lb fields. It does not specify closure or a maximum operating speed. A catalogue load rating is not an allowable application load.

Enduro model	Dynamic Cr	Static Cor	Mass
1601	2750 N	950 N	0.025 lb
1602	2750 N	950 N	0.025 lb
1603	3350 N	1410 N	0.033 lb
1604	3350 N	1410 N	0.040 lb
1605	3350 N	1410 N	0.034 lb
1606	3350 N	1410 N	0.035 lb
1607	4090 N	1960 N	0.060 lb
1614	5110 N	2380 N	0.077 lb
1615	5110 N	2380 N	0.071 lb
1616	5110 N	2380 N	0.066 lb
1620	6000 N	3250 N	0.110 lb
1621	6000 N	3250 N	0.106 lb
1622	6000 N	3250 N	0.101 lb
1623	6000 N	3250 N	0.088 lb
1628	8370 N	4520 N	0.159 lb
1630	8370 N	4520 N	0.143 lb
1633	8370 N	4520 N	0.203 lb
1635	8370 N	4520 N	0.187 lb
1638	10060 N	5920 N	0.265 lb
1640	10060 N	5920 N	0.247 lb
1641	10060 N	5920 N	0.221 lb
1652	16210 N	10420 N	0.463 lb
1654	16210 N	10420 N	0.419 lb
1657	16210 N	10420 N	0.474 lb
1658	16210 N	10420 N	0.441 lb

Keep RS, 2RS, ZZ and width suffixes distinct

The table records the publisher’s open, shielded or sealed column. An unlisted “RS” marking is not rewritten as “2RS”. Keep special endings such as W21, W23 or a fractional bore suffix: they can identify a different width or bore. No automatic cross-brand substitution is approved.

Metric values converted from printed inch decimals inherit the source rounding. For example, 0.2812 in converts to 7.14248 mm; that extra decimal detail is arithmetic, not a tolerance or a machining target. Never silently round an inch bearing into the nearest metric size. Missing speed, clearance, precision, internal ball diameter, material grade or exact lubricant remain unknown.

Publisher references: SMB product charts and Enduro 1600-series data; checked 2026-10-02. Original BearingScope interpretation. No stock, sales, vehicle fitment or redistributable CAD is implied. Material names describe the source page, not a certificate for every item sold under a similar number.

Metric and inch variant directory Main catalogue dimension finder Exact unit conversion Closure-selection guide

Why a closure suffix can change the bearing width

For the SMB 1604 entries, open and ZZ width is 0.2812 inch, while 1604-2RS is 0.3438 inch. For R6, the open row and the special R6-2RSW21 row are 0.2188 inch wide; the ordinary R6ZZ and R6-2RS rows are 0.2812 inch wide. Check the exact row instead of copying the base-model width.

The source designation, source unit and closure are separate fields. A metric conversion does not turn an inch-series item into a metric-series replacement. The extra decimals created by multiplication are not additional manufacturing accuracy.

Read dimensions and ratings as different kinds of evidence

The SMB charts used here identify nominal dimensions and closure variants. They do not provide a model-specific maximum speed, grease identity, clearance, ABEC class or complete controlled drawing in these extracted rows. No such field is invented.

Enduro’s 1600-series table separately reports dynamic Cr, static Cor and weight. Those figures stay with their own Enduro designation; they are not used to fill an empty SMB rating. The series table does not establish which closure is supplied.

RS, 2RS, ZZ and missing technical qualifiers

Does a search for RS automatically mean 2RS?

No. The records retain the publisher’s full designation and closure column. If the exact single-RS record is not present, it remains a data gap rather than being renamed as a two-seal item.

Does ZZ or 2RS establish ABEC, C3 or a lubricant grade?

No. Closure, running clearance, precision and lubrication are independent properties. Use evidence for the complete execution.

Are these pictures or drawings sufficient for machining?

No drawing or CAD has been generated or redistributed by this lookup. Nominal envelope values are not a toleranced manufacturing drawing.

Observation is not diagnosis

What the evidence can — and cannot — tell you

Observation or context	Interpretation to consider	Verification needed
A basic number only	Several closures can share the base	Read every suffix and all three dimensions.
Two equal diameters	Width may still differ	Compare the individual open, shielded and sealed rows.
A compact marking such as 16162RS	Spacing can hide a suffix boundary	Find the documented 1616-2RS row; do not treat it as an invented 16162 base.

A practical investigation sequence

Identify and record

Record the publisher or brand and the complete marking, including fractional bore and width suffixes.

Check the context

Filter the table to the source unit, material group and closure you actually need.

Verify before acting

Compare d, D and B together, preserving the printed values before converting units.

Keep the decision traceable

Use the actual product drawing and application requirements for fits, tolerances, speed, load and interchange decisions.

Capture the information a model search cannot guess

Keep this checklist with your inspection or comparison. Checking a box only records that you have collected the item; it does not certify the bearing.

Complete brand, designation and all suffixesMachine or vehicle identity and component positionMeasured values, units and operating conditionsPhotographs, drawing revision and source record

0 of 4 information groups recorded.

Technical basis & editorial scope

Original BearingScope workflow, written for catalogue research and comparison. Manufacturer material is used to check principles, not copied as a product endorsement or substituted for model-specific instructions. Reviewed 1 October 2026.

SMB — inch size chart — Factual full-designation table fields; original interpretation. Units and closure-specific widths retained. Reviewed 2026-10-02.
Enduro — 1600-series catalogue — Factual full-designation table fields; original interpretation. Units and closure-specific widths retained. Reviewed 2026-10-02.
SMB — miniature metric size chart — Factual full-designation table fields; original interpretation. Units and closure-specific widths retained. Reviewed 2026-10-02.
SMB — ball metric size chart — Factual full-designation table fields; original interpretation. Units and closure-specific widths retained. Reviewed 2026-10-02.
SMB — stainless inch size chart — Factual full-designation table fields; original interpretation. Units and closure-specific widths retained. Reviewed 2026-10-02.
SMB — stainless metric size chart — Factual full-designation table fields; original interpretation. Units and closure-specific widths retained. Reviewed 2026-10-02.

Source addresses and collection status are retained in the internal audit. No unpublished dimensions, torque settings, service intervals or interchange approvals are inferred.