Bearing Size Chart in mm: 6xx, 68x, 69x, MR & Flanged

Short answer: a bearing size is always given as bore x outer diameter x width in millimetres (d x D x B). A 623 is 3 x 10 x 4 mm, a 608 is 8 x 22 x 7 mm and an MR105 is 5 x 10 x 4 mm. The tables below list every size we stock, with links to the ZZ, 2RS and stainless versions. The seal suffix (ZZ or 2RS) never changes the dimensions.

How to read a bearing size chart

Every chart uses the same three numbers. d is the bore, the hole the shaft goes through. D is the outer diameter, which fits into the housing. B is the width. Flanged bearings add a fourth and fifth figure: the flange diameter and the flange width. These boundary dimensions are standardised internationally (ISO 15 for radial bearings), which is why a 623ZZ from one maker has the same size as a 623ZZ from another.

The closure is not part of the size. A 623ZZ, a 623-2RS and a stainless 623ZZ SS are all 3 x 10 x 4 mm. If you are unsure what the letters mean, see our guide how to read bearing codes.

How to measure a bearing size

1. Clean the bearing and read any code on the shield or the face of the outer ring first. If you can read it, look the code up below; that is more reliable than measuring.
2. Measure the bore with the inside jaws of a caliper, the outer diameter with the outside jaws and the width across the rings, not across the shields.
3. Round to the nearest standard value. Small bearings use whole millimetres or half millimetres (2.5 mm, 3.5 mm), so a reading of 3.98 mm is a 4 mm dimension.
4. If a figure looks like an inch size (for example 6.35 mm, which is 1/4 inch), you may have an inch-series bearing, which this chart does not cover.

6xx bearing size chart (623 to 627)

In the 62x miniature range, the last digit is the bore in millimetres. These are the "standard" width bearings, and the 623 is one of the most-used sizes in 3D printers and small mechanisms.

68x and 69x thin-section sizes

The 68x and 69x series share the bore of the matching 62x bearing but are thinner and smaller on the outside: 68x is the narrowest, 69x sits between 68x and 62x. Pick one of these when the housing is tight.

MR bearing sizes

MR bearings are metric miniature bearings in which the code gives the bore and the outer diameter: MR105 is 5 mm bore and 10 mm outside, MR128 is 8 mm and 12 mm. The width is not in the code, so check it in the table.

Flanged bearing size chart

A flanged bearing has a lip on the outer ring that locates it in the housing and stops it sliding through. F is the flanged version of a 6xx bearing, MF the flanged version of an MR bearing. Bore, outer diameter and width are the same as the non-flanged bearing.

608 and 6000/6200 series sizes

For larger bores, the 60 and 62 series use a bore code: from 04 upwards the bore is the code times 5 mm, while 00 is 10 mm, 01 is 12 mm, 02 is 15 mm and 03 is 17 mm. The 62 series is wider and heavier than the 60 series with the same bore, as the 6000 and 6200 below show. The 608 is the 8 mm bore bearing of the 60 series.

Linear bearings: LM UU sizes

LM UU linear ball bearings run along a smooth rod instead of turning on a shaft. The number is the rod diameter: LM6UU 6 x 12 x 19 mm, LM8UU 8 x 15 x 24 mm, LM10UU 10 x 19 x 29 mm, LM12UU 12 x 21 x 30 mm and the long LM8LUU 8 x 15 x 45 mm. The third figure is the length.

Buy bearings by size

Once you know d x D x B, the quickest route is the collection for that family: miniature ball bearings, MR series, flanged bearings, 608 bearings, deep groove 6000/6200 and linear bearings. Then choose the closure (ZZ or 2RS) and the material. Every product page repeats the dimensions, so you can double-check before ordering.

Related guides

• How to read bearing codes
• ZZ vs 2RS bearings
• 3D printer bearings

Sources

• ISO 15:2017, Radial bearings: boundary dimensions, general plan
• NSK, Bearing dimensions and designations (TI-0111)