I only have two Cosina SLR lenses (that's who makes the Zeiss isn't it?) and they seem really well built to me. The lenses are the 58mm 1.4 and Apo-Lanthar 90mm 3.5 in Nikon mount, both lenses have aperture and focusing actions that are superior to anything made by Nikon, beautifully damped. Leica of course are the benchmark, but the cost is astronomical.