Ruby coloured hand vases (and other glass items) are often misidentified as "ruby flash", when they are in fact "ruby stained". Flashing and casing involve adding a layer of glass over usually clear or white glass. Staining, however, is simply adding a layer of colour - the stain is "painted on".
The following vases pictured below have been partially stained ruby.
This pair of hand vases (below) has been completely stained ruby over clear glass.
These ruby stained hand vases look distinctly different from vases which have been made from ruby glass (below). Ruby glass is much darker. Ruby stained vases are often lighter or transparent and the stain may rub off with age.
For more information on flashed vs. stained vs. cased glass go to http://www.patternglass.com/FlashCaseStain/FlashCaseStain.htm