I have checked several items and I have measured 4mm. The inner diameter of these bearings is much larger than any item I have measured and is 4mm. I agree with other reviews, these stock measurements are wrong.
Bearing 608- ZZ1MC3E (8x22x7) NSK//80018
4 Review
Enhanced Performance Sydien SCS12UU Bearing Bushing Diameter for Precision Machinery
4 Review
π§ High-Quality TIMKEN 6203 2RSC3 6203 2RS Bearing - Size: 17X40X12mm
4 Review
π Wheels Manufacturing Ball Retainer Bag: Convenient Storage and Protection for Your Ball Retainers
6 Review