Bearing closures are available in two basic types - shields and seals. Both closure types are generally ordered as integral components of deep groove bearings.
Closures serve the same purposes with varying effectiveness - they exclude contamination, contain lubricants and protect the bearing from internal damage whilst being handled.
Closures are attached to the outer ring of the bearing. Seals are defined as closures which contact the inner ring, while shields clear the inner ring. Both are designed so that the stringent precision tolerances are not affected by their use.