This sale is for a really excellent condition Mamiya RZ67 / RB67 rear lens cap, suitable for use with all RB67 and RZ67 lenses except the RB67 50mm (where you need a special deeper cap because the rear element sticks out too much). Plenty available – if you want more just ask.
This cap is in great condition with just the usual slight signs of use. Try finding another one – these are almost impossible to find.