Vivitar 100-300mm f5 Close Focus Auto Zoom lens Minolta mount Max. Aperture: f5; Mini. Aperture: f22; optical construction: 13 elements/ 9 group Read more at: http://www.pentaxforums.com/userreviews/vivitar-100-300mm-f5-constant-auto-tx-close-focusing-zoom.html#ixzz2yt58eF5w 43cm at close-focus weight: 804g (28.4oz)