This is a 2 pack of NMB 8mm x 16mm x 5mm bearings. The NMB bearings have a steel shields and a light oil so there is very little drag on the bearing. Please check out both videos for additional information on the Mugen NMB bearings.

https://www.youtube.com/watch?v=CUQ_H77NDN8

https://www.youtube.com/watch?v=QrPJFox7gqQ