Bearing Guides

Four shielded ball bearings in decreasing sizes with a measuring line under the largest one.
Bearing Size Lookup and How to Measure a Bearing
How to measure a bearing with a caliper and find it by bore, outer diameter and width in one mm lookup table. Read more...
A straight steel dowel pin next to a darker tapered pin, labelled Dowel pin and Taper pin.
Dowel Pin vs Taper Pin: When to Use Which
Dowel pin or taper pin? How they differ, which ISO standards apply, how to size the hole and when to use each. Read more...
Two ball bearings side by side, one with grey metal shields labelled 608ZZ and one with black rubber seals labelled 608-2RS.
608ZZ vs 608-2RS (and 608 Open): Which to Buy
608ZZ, 608-2RS and an open 608 are the same 8 x 22 x 7 mm bearing with different closures. Which one to buy, compared in one table. Read more...
623ZZ SS stainless steel 440C miniature bearing 3x10x4 mm
Stainless Steel vs Chrome Steel Bearings: 440C vs 52100
Chrome steel bearings (AISI 52100, also called GCr15 or 100Cr6) are the standard choice: hard, strong and economical, but they rust if they get wet. Stainless steel bearings (usually AISI... Read more...
LM8UU linear ball bearing 8x15x24 mm for 8 mm rods
3D Printer Bearings: LM8UU, 608, 623ZZ & F623ZZ Explained
Most hobby 3D printers use four kinds of bearing. LM8UU linear bearings (8 x 15 x 24 mm) slide along 8 mm smooth rods. 623ZZ (3 x 10 x 4... Read more...
10 mm chrome steel precision ball, grade G10
Steel Ball Grades Explained: G5, G10, G28 (ISO 3290)
A ball grade such as G10 tells you how round and how consistent a precision ball is. The lower the number, the tighter the tolerances: a G5 ball is rounder... Read more...
MR105-2RS miniature ball bearing 5x10x4 mm with rubber seals
How to Read Bearing Codes: 623ZZ, MR105-2RS, F608ZZ
A bearing code is built from a prefix (type or material), a series number, a bore code and a suffix (shields, seals and other options). In 623ZZ, "62" is the... Read more...
623ZZ bearing dimension drawing: bore 3 mm, outer diameter 10 mm, width 4 mm
Bearing Size Chart in mm: 6xx, 68x, 69x, MR & Flanged
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... Read more...
608ZZ miniature ball bearing 8x22x7 mm with ZZ metal shields
ZZ vs 2RS Bearings: Shields vs Seals, Which to Choose
A ZZ bearing has a thin metal shield on each side that does not touch the inner ring, so it runs with low friction and suits higher speeds in clean,... Read more...