These are knurled nuts respectively with a diameter of 42 mm for the reference BPF196 and a diameter of 50 mm for the reference BPF 197. These are 12 mm thick through nuts.
The knurling allows manual tightening. It is very durable and corrosion resistant. It doesn't conduct electricity.
This quick release knurled nut is good industrial quality.
These knurled nuts are used in the furniture, construction and aerospace industries.