This is the Pentax K-mount version of the Helios 44-4. I purchased it here, but I'm selling it because I don't use it much. The optics are clean with only minor dust, and there is no mold or fogging that would affect the image quality. The focus ring is a little stiff, but there are no snags and it works fine. Please understand that this is a used item before purchasing. MC HELIOS-44K-4 lens, 58mm f/2, Pentax K-mount, 16 aperture blades, minimum focusing distance 0.5m. - Brand: ZENIT - Model: MC HELIOS-44K-4 - Focal Length: 58mm - Maximum Aperture: f/2 - Aperture Blades: 16 - Minimum Focusing Distance: 0.5m - Filter Diameter: M52 Thank you for looking.