Inch Series (R) Bearings — Size Chart
Inch-series (R) bearings are single-row deep groove ball bearings made to fractional-inch dimensions instead of whole millimetres. This page lists all 21 sizes we cover, from the tiny R09 up to the R6, with dimensions in inches and millimetres, basic load ratings and limiting speeds. Shielded versions (ZZ or ZZS) are shown next to each open bearing; some are wider than the open version.
Reading the number: in the main R2 to R6 family the number after the R is the bore in sixteenths of an inch, so an R4 has a 4/16 = 1/4 in bore and an R6 a 6/16 = 3/8 in bore. Miniature designations such as R144, R188 or R1810 follow a different code, so go by the dimensions in the table rather than the number.
Not interchangeable with metric sizes: an inch bearing will not correctly fit a metric shaft or housing of a similar size. The R numbers are widely used across manufacturers, but always compare the dimensions and suffixes with the catalogue of the manufacturer before ordering.
Measured a bearing in inches? Enter the sizes in the Bearing Finder, or compare inch and metric sizes side by side in the Bearing Size Chart. See also how to read bearing numbers and 2RS vs ZZ seals.
| Bearing | Bore × OD × Width (in) | Metric (mm) | Dynamic Load | Speed (Grease) | Shielded Version |
|---|---|---|---|---|---|
| R09 | 0.04 × 1/8 × 3/64 in | 1.016 × 3.175 × 1.191 mm | 0.105 kN | 130,000 rpm | — |
| R0 | 3/64 × 5/32 × 1/16 in | 1.191 × 3.967 × 1.588 mm | 0.153 kN | 110,000 rpm | R0ZZ (3/32 in wide) |
| R1 | 0.055 × 3/16 × 5/64 in | 1.397 × 4.762 × 1.984 mm | 0.255 kN | 90,000 rpm | R1ZZ (7/64 in wide) |
| R1-4 | 5/64 × 1/4 × 3/32 in | 1.984 × 6.35 × 2.38 mm | 0.34 kN | 67,000 rpm | R1-4ZZ (9/64 in wide) |
| R133 | 3/32 × 3/16 × 1/16 in | 2.38 × 4.762 × 1.588 mm | 0.208 kN | 80,000 rpm | R133ZZS (3/32 in wide) |
| R1-5 | 3/32 × 5/16 × 7/64 in | 2.38 × 7.938 × 2.779 mm | 0.605 kN | 60,000 rpm | R1-5ZZ (9/64 in wide) |
| R144 | 1/8 × 1/4 × 3/32 in | 3.175 × 6.35 × 2.38 mm | 0.31 kN | 67,000 rpm | R144ZZ (7/64 in wide) |
| R2-5 | 1/8 × 5/16 × 7/64 in | 3.175 × 7.938 × 2.779 mm | 0.615 kN | 60,000 rpm | R2-5ZZ (9/64 in wide) |
| R2-6 | 1/8 × 3/8 × 7/64 in | 3.175 × 9.525 × 2.779 mm | 0.705 kN | 53,000 rpm | R2-6ZZS (9/64 in wide) |
| R2 | 1/8 × 3/8 × 5/32 in | 3.175 × 9.525 × 3.967 mm | 0.695 kN | 56,000 rpm | R2ZZ (same width) |
| R2A | 1/8 × 1/2 × 11/64 in | 3.175 × 12.7 × 4.366 mm | 0.705 kN | 53,000 rpm | R2AZZ (same width) |
| R155 | 5/32 × 5/16 × 7/64 in | 3.967 × 7.938 × 2.779 mm | 0.395 kN | 53,000 rpm | R155ZZS (1/8 in wide) |
| R156 | 3/16 × 5/16 × 7/64 in | 4.762 × 7.938 × 2.779 mm | 0.395 kN | 53,000 rpm | R156ZZS (1/8 in wide) |
| R166 | 3/16 × 3/8 × 1/8 in | 4.762 × 9.525 × 3.175 mm | 0.78 kN | 50,000 rpm | R166ZZ (same width) |
| R3 | 3/16 × 1/2 × 5/32 in | 4.762 × 12.7 × 3.967 mm | 1.43 kN | 43,000 rpm | R3ZZ (0.196 in wide) |
| R168B | 1/4 × 3/8 × 1/8 in | 6.35 × 9.525 × 3.175 mm | 0.46 kN | 48,000 rpm | R168BZZ (same width) |
| R188 | 1/4 × 1/2 × 1/8 in | 6.35 × 12.7 × 3.175 mm | 1.19 kN | 40,000 rpm | R188ZZ (3/16 in wide) |
| R4B | 1/4 × 5/8 × 0.196 in | 6.35 × 15.875 × 4.978 mm | 1.77 kN | 38,000 rpm | R4BZZ (same width) |
| R4AA | 1/4 × 3/4 × 7/32 in | 6.35 × 19.05 × 5.558 mm | 2.88 kN | 36,000 rpm | R4AAZZ (9/32 in wide) |
| R1810 | 5/16 × 1/2 × 5/32 in | 7.938 × 12.7 × 3.967 mm | 0.595 kN | 40,000 rpm | R1810ZZ (same width) |
| R6 | 3/8 × 7/8 × 7/32 in | 9.525 × 22.225 × 5.558 mm | 3.65 kN | 32,000 rpm | R6ZZ (9/32 in wide) |
Dimensions, basic dynamic load ratings and grease limiting speeds from the NSK inch-series catalogue. Values for other manufacturers may differ slightly. Always verify dimensions, suffixes and clearance before ordering.