Olympus teleconverter TCON17 1.7x magnification Also known as B300, Fits 55mm filter thread or others with a suitable stepping ring. Lens in perfect condition with crystal clear optics. Original Olympus front and rear push on caps are a soft polythene material and have some slight marking, sound, nothing horrid. I have had good results using this lens on a variety of cameras, From my original Olympus C3020 and on lenses like Canon 70-200 f4L (on APSC) and Panasonic 45-175 (on micro 4/3). The advantage over a rear mounted converter is no loss of light.