The popular F608Z  flanged ball bearing with inner diameter of 8 mm. It is used in many applications including 3d printers. You can also use 2 bearings as idler pulley.

• Bore Dia (d):                        8 mm
• Outer Dia (D):                      22 mm
• Flange Dia (Df):                   25 mm
• Flange Width (Wfs):              1mm
• Material:                               52100 Chrome steel
• Dynamic Load Rating:        2800 (Newtons)
• Static Load Rating:             1100 (Newtons)
• Max Speed:                          35000 RPM
• Weight:                                14.20    (grams)