Instead of buying individual Bay-1 filters, you can also obtain Bay-1 - to screw mount filter adapters.
These adapters will allow you to use common screw mount filters that you may already have, and
with the use of step-up/step-down rings, you can fit just about any filter and rubber hood size you have.
An example of Bay-1 adapter-to-screw mount w/round hood:
Bay-1 to 30.5mm:
Bay-1 to 46mm:
Bay-1 to 49mm:
Bay-1 to 52mm: