Designation system
The designations of SKF super-precision bearings follow a system that consists of a basic designation with or without one or more prefixes and/or suffixes.
Examples and the applicable options for cylindrical roller bearings are given below.

Examples
Single row bearing | |||
N 1016 KPHA/HC5SP | where | N 1016 = | ![]() |
K = | ![]() |
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PHA = | ![]() |
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HC5 = | ![]() |
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SP = | ![]() |
Double row bearings | |||
NN 3020 KTN9/SPVR521 | where | NN 3020 = | ![]() |
K = | ![]() |
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TN9 = | ![]() |
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SP = | ![]() |
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VR521 = | ![]() |
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NNU 49/500 B/SPC3W33X | where | NNU 49/500 = | ![]() |
B = | ![]() |
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SP = | ![]() |
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C3 = | ![]() |
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W33X = | ![]() |
![]() | Prefixes (n.a.) |
![]() | Basic designation |
Bearing design | |
N | Single row cylindrical roller bearing |
NN | Double row cylindrical roller bearing |
NNU | Double row cylindrical roller bearing |
Dimension series | |
10 | In accordance with ISO dimension series 10 |
30 | In accordance with ISO dimension series 30 |
49 | In accordance with ISO dimension series 49 |
Bearing size | |
05
to 92 | (x5) 25 mm bore diameter
(x5) 460 mm bore diameter |
from
/500 |
Bore diameter uncoded [mm] |
![]() | Suffixes - Internal design and bore shape |
– | Cylindrical bore (no designation suffix) |
B | Modified internal design |
K
| Tapered bore, taper 1:12 |
![]() | Suffixes - External design (seals, snap ring groove etc.) (n.a.) |
![]() | Suffixes - Cage design |
–
| Machined brass cage, roller centred (no designation suffix) |
PHA | Carbon fibre reinforced PEEK cage, outer ring centred |
TN
| PA66 cage, roller centred
|
TN9
| Glass fibre reinforced PA66 cage, roller centred
|
TNHA | Glass fibre reinforced PEEK cage, outer ring centred |
![]() | Suffixes - Materials, heat treatment |
– | Carbon chromium steel (no designation suffix) |
HC5 | Rollers made of bearing grade silicon nitride Si3N4 (hybrid bearing) |
![]() | Suffixes - Accuracy, clearance, preload, quiet running | |
Accuracy | ||
SP | Dimensional accuracy in accordance with ISO tolerance class 5, running accuracy in accordance with ISO tolerance class 4 | |
UP | Dimensional accuracy in accordance with ISO tolerance class 4, running accuracy better than ISO tolerance class 4 | |
Internal clearance
|
||
– | Standard radial internal clearance C1 (no designation suffix) | |
C2 | Radial internal clearance greater than C1 | |
CN | Normal radial internal clearance | |
C3 | Radial internal clearance greater than Normal |
![]() | Suffixes - Bearing sets, matched bearings (n.a.) |
![]() | Suffixes - Stabilization (n.a.) |
![]() | Suffixes - Lubrication |
W33 | Annular groove and three lubrication holes in the outer ring |
W33X | Annular groove and six lubrication holes in the outer ring |
![]() | Suffixes - Other variants |
VR521 | Bearing supplied with measuring report (standard for NN 30 series bearings with d > 130 mm) |
VU001 | Inner ring raceway with finish-grinding allowance |