I have the 80, 180 and a 300 MC (the 50 Flektagon lost out to a 55 Russian) and, after my Pentagon 6 expired, got adapters for Mamiya 645 and even Nikon. The 180 f/2.8 is a great lens, even my old zebra one, and excellent for long range macro. The 300 f/4 is beautiful and is even a killer with a good 2x extender for 600 f/8. The lenses were of a much higher quality than the Pentagon 6 unfortunately.