Title says it all, does anybody know the required ferrule size for a Ryoma D1 driver?

Thanks in advance

Ryoma takes a .335 shaft so look for a corresponding ferrule.

Thanks does anyone know what the outside measurement of the hosel and if a counter sunk ferrule is recommended?

Counter sunk or collar ferrule is not needed. Not sure what the outer diameter is but n concern there as it can be easily turned down to size.