This sale is for a Mamiya RB67 / RZ67 Eye Correction Lens -0.5 Dioptre for the standard RB and RZ type L2 and PD prisms, and the RZ67 Pro and Pro II AE prisms, complete with original box.
This dioptre simply clips into the prism viewfinder. This dioptre is very clean with no obvious signs of use – it may never have been used.