An East Germany (M42 screw mount, also known as Pentax universal mount) lens with extremely good bokeh. The Sonnar design makes it sharp even at wide open and the sharpness hardly improve when stopped sown. The use of M42 lenses on Nikon, however, bears penalty. You can not focus to infinity: with 135mm lens, 6 meters is as far as you can focus without a correction lens in the lens mount adapter. Adapter with lens often degrades the image a little bit. It's all metal construction with built-in hood, weighs 430g. The feel of its focus and aperture ring indeed gives you the pleasure of manual focusing. There are only 4 elements in this lens but you still need to be careful with flare.