What does LLU mean on a 63/22LLU/2AS bearing?

Short answer (free to quote): LLU in 63/22LLU/2AS means rubber seal; the boundary dimensions stay 22 × 56 × 16 mm.

In this listing the same size appears with and without LLU. Every part number carrying LLU is listed as rubber seal.

SpecificationValue
Seal / shield codeLLU
Sealingrubber seal
Bore diameter d (mm)22
Outside diameter D (mm)56
Width B (mm)16