You can use RB67 lenses ("L" series) on the RZ67, but can't use RZ67 ("Z" series) on the RB67. You can find Mamiya Sekor KL 90mm f/3.5 L lenses on Ebay pretty often although the KL 127mm f/3.5 L is much more common. Actually I'm not all that impressed with my KL 90mm lens, it the field of view of a 44mm lens on a 35mm camera. The KL 127mm (62mm equivalent on a 35mm camera) seems more useful. The KL 127mm is pretty reasonable; a dealer in Michigan is selling them new in the box for $150.