In The Netherlands, in schools 23-ring-binders are quite heavily used. In office environments it is mostly 2- or 4. The nice thing is that they are compatible:

In The Netherlands, in schools 23-ring-binders are quite heavily used. In office environments it is mostly 2- or 4. The nice thing is that they are compatible: if you have 23-ring-paper or 4-ring it will fit in 2 or 4 ring binders. This does not work the other way around for obvious reasons.