6203, 6203-ZZ and 6203-2RS are the same size: 17 mm bore, 40 mm outside diameter and 12 mm wide. The letters after the number tell you how the bearing is closed.
The suffixes
- 6203 (open) has no seals or shields. It is used where the bearing is lubricated by oil in a gearbox or greased from outside.
- 6203-ZZ (also written 2Z) has a metal shield on both sides. Shields keep out larger dirt and run with very little friction, so they suit higher speeds.
- 6203-2RS (also 2RSH or DDU) has a rubber seal on both sides. Seals touch the inner ring and keep out water and fine dust, at the cost of a little more friction.
- Z or RS with one letter means only one side is closed.
Which one to choose
For a clean, dry, fast-running motor, ZZ is usually right. For dusty, wet or outdoor equipment such as pumps, farm machinery and washing machines, choose 2RS. Use an open bearing only when it runs in oil.
Other suffixes you will see
C3 means more internal clearance than normal, used where the bearing runs hot, as in many electric motors. K means a tapered bore. E means a higher-capacity internal design on roller bearings. M or MB means a brass cage.
If you are not sure, send us the full number off the old bearing, including every letter.
