Emily........ You'll find the Series # expressed as a Roman Numeral on the edge of the filter......along with the actual filter type (#)....... The Series filter and filter rings allowed a single set of filters to be used on different lenses with different sized front elements.......and because each filter or attachment was plain they were cheaper to manufacture than individual threaded filters........A Series VII filter might fit into/on 49mm lens filter ring and also a 52mm ring or the odd sized(but ever popular) 40.5mm ring.....same filter-different rings A common set would include a red, yellow , orange, green......maybe a color correction filter or two ........and those CLOSE-UP filters (+1,+2,+3) allow the lens to focus closer than normal......all stashed in the nifty little leatherette case.......I also have some classic clear plastic cases that consist of a circular "drawer"....and the cases have male/female bayonets top and bottom so you could stack all your filter collection together.......... doug __________________________________________________ Do you Yahoo!? Faith Hill - Exclusive Performances, Videos & More http://faith.yahoo.com
