F608ZZ Flanged Deep Groove Single Row Ball Bearing.
Inner Diameter: d = 8mm
Outer Diameter: D = 22mm
Width: B = 7mm
Flange Diameter: D1 = 25mm
Flange Thickness: B1 = 1.5mm
Material: Chrome steel GCr15
This size is used in some designs of Reprap.
The ZZ designation is for metal side shields. These offer lower rolling resistance than 2RS style but less protection from dust and moisture.