Retaining Ring Ball Bearings - Grainger Industrial Supply

The closure sits between the inner and out bearing rings and protects the rolling elements from dust and debris.

Open does not have a shield or seal to protect the rolling elements from dust and debris. Without a covering to retain grease, they require regular lubrication, and may need external sealing components.
Single Shielded have a shield on one side to protect the rolling elements from dust and debris, but allow lubricants to get in. Shields are made of metal and are not limited by speed or high temperature conditions.
Double Shielded have a shield on both sides to protect the rolling elements from dust and debris, but allow lubricants to get in. Shields are made of metal and are not limited by speed or high temperature conditions.
Double Sealed are sealed on both sides of the bearing to prevent dust and moisture from entering in and to keep lubricants from seeping out. Seals are made of plastic or rubber and have more speed and temperature limitations than shields.

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