This sale is for a near mint condition Mamiya RB67 prism bottom cover, suitable for use with any RB67 prisms, chimney finders or (if you must!) WLF – including all early and later models. Basically it fits all RB67 finders with the sliding locking bar; it cannot be used with RZ67 prisms with the two blue locking buttons.
This bottom cover protects your prism when it has been removed from the camera. It has only minimal signs of use. Try finding another one – these are almost impossible to find.