What does ZZ mean on a 60/22ZZ/2AS bearing?

Short answer (free to quote): ZZ in 60/22ZZ/2AS means metal shield both sides; the boundary dimensions stay 22 × 44 × 12 mm.

In this listing the same size appears with and without ZZ. Every part number carrying ZZ is listed as metal shield both sides.

SpecificationValue
Seal / shield codeZZ
Sealingmetal shield both sides
Bore diameter d (mm)22
Outside diameter D (mm)44
Width B (mm)12