An insert bearing is the ball bearing that sits inside a pillow block or flange housing, and its UC number gives the bore: a UC205 takes a 25 mm shaft and a UC210 a 50 mm shaft. Its outside is spherical, so it can align in the housing, and its wide inner ring locks to the shaft with grub screws.
Our imperial inserts add a dash number, the bore in sixteenths of an inch, so our 1 inch insert is a UC205-16. Find your size in the table below, or start from your shaft in the lookup under it.
UC insert bearing sizes: bore, outside diameter and width
Every UC insert we list, with its bore, outside diameter (D) and inner ring width (B). An imperial insert has the same D and B as the metric insert on its row.
| Insert | Metric bore | Imperial bores we list | Outside diameter D | Inner ring width B | Our UCP, UCF and UCFL units |
|---|---|---|---|---|---|
| UC201 | 12 mm | 1/2" (UC201-8) | 47 mm | 31 mm | Every bore |
| UC202 | 15 mm | 5/8" (UC202-10) | 47 mm | 31 mm | Every bore |
| UC203 | 17 mm | None | 47 mm | 31 mm | Every bore |
| UC204 | 20 mm | 3/4" (UC204-12) | 47 mm | 31 mm | Every bore |
| UC205 | 25 mm | 7/8" (UC205-14), 1" (UC205-16) | 52 mm | 34.1 mm | Every bore |
| UC206 | 30 mm | 1-1/8" (UC206-18), 1-3/16" (UC206-19), 1-1/4" (UC206-20) | 62 mm | 38.1 mm | Every bore |
| UC207 | 35 mm | 1-1/4" (UC207-20), 1-3/8" (UC207-22), 1-7/16" (UC207-23) | 72 mm | 42.9 mm | Every bore |
| UC208 | 40 mm | 1-1/2" (UC208-24) | 80 mm | 49.2 mm | Every bore |
| UC209 | 45 mm | 1-5/8" (UC209-26), 1-3/4" (UC209-28) | 85 mm | 49.2 mm | Every bore, plus 1-11/16" (209/27) |
| UC210 | 50 mm | 1-7/8" (UC210-30), 1-15/16" (UC210-31), 2" (UC210-32) | 90 mm | 51.6 mm | Every bore |
| UC211 | 55 mm | 2" (UC211-32), 2-1/8" (UC211-34), 2-3/16" (UC211-35) | 100 mm | 55.6 mm | Every bore |
| UC212 | 60 mm | 2-1/4" (UC212-36), 2-3/8" (UC212-38), 2-7/16" (UC212-39) | 110 mm | 65.1 mm | Every bore except 2-3/8" |
| UC213 | 65 mm | 2-1/2" (UC213-40) | 120 mm | 65.1 mm | Not listed |
| UC214 | 70 mm | 2-3/4" (UC214-44) | 125 mm | 74.6 mm | Not listed |
| UC215 | 75 mm | 3" (UC215-48) | 130 mm | 77.8 mm | Not listed |
| UC216 | 80 mm | None | 140 mm | 82.6 mm | Not listed |
| UC217 | 85 mm | None | 150 mm | 85.7 mm | Not listed |
| UC218 | 90 mm | 3-1/2" (UC218-56) | 160 mm | 96 mm | Not listed |
Source: a bearing maker's published UC2 insert table (see Sources), read 30 October 2026. Every figure matches the bore, outside diameter and insert width in our listings' specifications. Housings: our UCP, UCF and UCFL listings.
How to read a UC number
Take a UC205-16 from left to right:
- UC is the bearing type: a ball bearing insert that locks to the shaft with set screws, which we call grub screws.
- 2 is the series. Every UC insert we list is a 200 series insert.
- 05 is the bore code, read the same way as on a 6200 ball bearing (see our bearing size chart): 01 = 12 mm, 02 = 15 mm, 03 = 17 mm, and from 04 up multiply by 5, so 05 = 25 mm, 10 = 50 mm and 18 = 90 mm.
- -16 is the imperial bore in sixteenths of an inch, as our part numbers write it: 16/16 is 1 inch, -8 is 1/2", -12 is 3/4", -20 is 1-1/4" and -32 is 2". Some makers number inch bores differently, so go by the inch size on the listing. The dash number changes the bore only. The outside diameter and width stay those of the UC205.
Our UC insert listings write the dash (UC205-16), and most of our housing and stainless listings a slash (UCP205/16, SUC205/16). It's the same bore.
Why a UC205 isn't a 6205
A UC205 has the same 25 mm bore and 52 mm outside diameter as a 6205 ball bearing, but its inner ring is 34.1 mm wide against the 6205's 15 mm, it carries the grub screws, and its outside is spherical so it can sit in the housing's spherical bore. Sealed (2RS) or shielded (ZZ) makes no difference to that: a 6205 is a different bearing (our seal codes guide explains those suffixes). If the bearing you took out is 25 x 52 mm with a wide inner ring and grub screws, it's a UC205.
Which insert fits my shaft?
For a metric shaft, the shaft size is the metric bore in the table: a 25 mm shaft takes a UC205, a 40 mm shaft a UC208, a 60 mm shaft a UC212. Measure it with vernier callipers: 25.0 mm is a UC205, but 25.4 mm is 1 inch, a UC205-16.
For an imperial shaft, find it below (1 inch = 25.4 mm exactly):
| Shaft | Shaft in mm | Our insert |
|---|---|---|
| 1/2" | 12.7 | UC201-8 |
| 5/8" | 15.875 | UC202-10 |
| 3/4" | 19.05 | UC204-12 |
| 7/8" | 22.225 | UC205-14 |
| 1" | 25.4 | UC205-16 |
| 1-1/8" | 28.575 | UC206-18 |
| 1-3/16" | 30.1625 | UC206-19 |
| 1-1/4" | 31.75 | UC206-20 or UC207-20 |
| 1-3/8" | 34.925 | UC207-22 |
| 1-7/16" | 36.5125 | UC207-23 |
| 1-1/2" | 38.1 | UC208-24 |
| 1-5/8" | 41.275 | UC209-26 |
| 1-11/16" | 42.8625 | No loose insert; UCP209/27, UCF209/27 or UCFL209/27 unit |
| 1-3/4" | 44.45 | UC209-28 |
| 1-7/8" | 47.625 | UC210-30 |
| 1-15/16" | 49.2125 | UC210-31 |
| 2" | 50.8 | UC210-32 or UC211-32 |
| 2-1/8" | 53.975 | UC211-34 |
| 2-3/16" | 55.5625 | UC211-35 |
| 2-1/4" | 57.15 | UC212-36 |
| 2-3/8" | 60.325 | UC212-38 |
| 2-7/16" | 61.9125 | UC212-39 |
| 2-1/2" | 63.5 | UC213-40 |
| 2-3/4" | 69.85 | UC214-44 |
| 3" | 76.2 | UC215-48 |
| 3-1/2" | 88.9 | UC218-56 |
Source: our product listings; millimetres converted by us from the inch bores.
Two shaft sizes come in two insert sizes. A 1-1/4" shaft takes a UC206-20 (62 mm outside) or a UC207-20 (72 mm), and a 2" shaft a UC210-32 (90 mm) or a UC211-32 (100 mm). The shaft can't tell you which, so read the number on the old insert or measure its outside diameter, and match the housing you already have.
Which housing takes which insert?
The housing number is the insert number with the housing letters added. A UCP205 pillow block, a UCF205 four-bolt flange and a UCFL205 two-bolt flange all carry a UC205, and a UCP205/16 carries a UC205-16. Our UCP vs UCF vs UCFL guide compares the three housings, and the UCP204 to UCP206 dimensions give the bolt centres and centre heights.
As our listings pair them:
- UC201 to UC212: we list every bore in the table above as a UCP, UCF and UCFL unit, with two exceptions. 2-3/8" (UC212-38) we list as the insert only. 1-11/16" (209/27) we list as UCP, UCF and UCFL units, but not as a loose insert.
- UC213 to UC218: we list the inserts only, not UCP, UCF or UCFL units.
Our take-up units (UCT201 to UCT215, metric bores) carry the UC insert of the same number.
Our units arrive with the insert already fitted, though you may need to align it for your job. Our inserts are C3 clearance and lock with grub screws. Some makers' inserts lock with an eccentric collar instead; we don't stock those, but our team can source them on request.
If the housing is sound and only the bearing is worn, replace just the insert. Our guide to getting an insert bearing into a housing shows how it goes in.
Stainless steel inserts (SUC)
Our stainless steel inserts carry an S in front: SUC202 to SUC213, with the 3/4", 1", 1-1/4", 1-1/2", 1-3/4", 2" and 2-1/2" bores (SUC204-12, SUC205-16, SUC207-20, SUC208-24, SUC209-28, SUC211-32 and SUC213-40). Each is listed at the same bore, outside diameter and width as the UC insert of the same number. Most stainless listings are single inserts; the UC listings are pairs.
We don't list UC300 series inserts. Our SB bearings are listed for go-karts and Cox mowers, and our go-kart axle bearing guide covers the kart sizes.
Which Bearings Express insert to pick
- Pick the UC201 to UC207 insert listing for any metric or imperial size from 12 mm to 1-7/16", on one page.
- Pick the UC208 to UC209 insert listing for 40 mm, 45 mm, 1-1/2", 1-5/8" or 1-3/4".
- Pick the UC210 to UC218 insert listing for 50 to 90 mm and the imperial bores from 1-7/8" to 3-1/2".
- Pick the UC210 50 mm insert pair for a 50 mm shaft with a 90 mm outside diameter.
- Pick the UC205-16 1" insert pair for a 1" shaft in a 205 housing.
- Pick the SUC202 to SUC207 stainless inserts if the job calls for stainless steel. The larger stainless sizes are in the collection.
Every insert and housing is in insert and transmission bearings. Ordering, delivery and returns questions are answered in our FAQ.
Questions people also ask
What are the UC210 bearing dimensions?
50 mm bore, 90 mm outside diameter and a 51.6 mm wide inner ring. The imperial UC210-30, UC210-31 and UC210-32 (1-7/8", 1-15/16" and 2") have the same outside diameter and width, and all four fit the 210 housings (UCP210, UCF210, UCFL210).
What is a 1 inch insert bearing?
A UC205-16: a 1" (25.4 mm) bore with the UC205's 52 mm outside diameter and 34.1 mm inner ring, so it fits the same 205 housings as the 25 mm UC205.
What are the UCP212 bearing dimensions?
A UCP212 pillow block carries the UC212 insert (60 mm bore). Our UCP212 listing gives a 69.8 mm centre height, 184 mm bolt centres, 241 mm overall length, a 70 mm wide base and 20 mm bolt holes for M16 bolts. Our UCP212/36 and UCP212/39 listings give the same housing figures.
What does UC mean on a bearing?
UC is the bearing type code for an insert that locks to the shaft with set screws (grub screws). The letters after it, such as P, F or FL, name the housing, so a UC205 on its own is the insert, and a UCP205 is that insert in a pillow block.
Related reading
- UCP vs UCF vs UCFL: pillow block or flange bearing, which housing do I need?
- UCP204, UCP205, UCP206 pillow block dimensions
- How to get an insert bearing into a housing
- 16 mm and imperial bore ball bearings: 6202-10, 6203-12, 6204-16 and the rest
Sources
- NTN, Bearing Units, Cat. No. 2400/E, UC2 ball bearings, set screw type: dimension tables pp. 414, 416 and 418, https://www.ntnglobal.com/en/products/catalog/pdf/2400E_07.pdf, read 30 October 2026.
- NTN, Bearing Units, Cat. No. 2400/E, technical data: construction (p. 11), self-aligning (p. 13), part numbering (p. 16), https://www.ntnglobal.com/en/products/catalog/pdf/2400E_03.pdf, read 30 October 2026.
- NTN, Bearing Units, Cat. No. 2400/E, UCP2 pillow block table (p. 64), https://www.ntnglobal.com/en/products/catalog/pdf/2400E_04.pdf, read 30 October 2026.
- Bearings Express product listings: UC and SUC insert listings and the UCP, UCF and UCFL listings in insert and transmission bearings, read 30 October 2026.
Checked against the NTN Bearing Units catalogue, our team's answers and Bearings Express product listings on 30 October 2026.
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