The Vivitar 70-300mm f/4.2-5.8 extended the brand's telephoto zoom range further than its 70-210mm and 80-200mm siblings, sold as a long-reach consumer option for manual-focus SLR owners wanting extra telephoto reach without a dedicated super-telephoto.
It is a manual-focus zoom with a maximum aperture narrowing from f/4.2 at 70mm to f/5.8 at 300mm, offered across the principal manual-focus SLR fittings sold through independent camera dealers. Its manufacturer, filter thread, weight and minimum focus distance are not confirmed from available sources.
The extended 300mm reach comes at the cost of a slow maximum aperture at the long end, and like most budget superzooms of its generation it is at its best stopped down, with softer corners and reduced contrast wide open, especially past 200mm.
It is an inexpensive route into longer telephoto reach on the used market. Check the zoom mechanism for smooth, grit-free travel, confirm the tripod collar or mount is undamaged where fitted, and inspect the rear elements for haze.