http://cgi.ebay.com/BRIDGEPORT-SLOTTING-SHAPING-HEAD-ATTACHMENT-MDL-E_W0QQitemZ150237775822QQihZ005QQcategoryZ104242QQ tcZphotoQQcmdZViewItem (http://cgi.ebay.com/BRIDGEPORT-SLOTTING-SHAPING-HEAD-ATTACHMENT-MDL-E_W0QQitemZ150237775822QQihZ005QQcategoryZ104242QQ tcZphotoQQcmdZViewItem)

It looks like it tuns a mill into a bayonet saw.
What do you use it for.

You need this:
http://cgi.ebay.com/ROMI-BRIDGEPORT-EZ-PATH-16-5-x-40-CNC-MANUAL-LATHE_W0QQitemZ150237133440QQihZ005QQcategoryZ9723 0QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

JR,

It's for cutting internal splines, keyways or slots. Unless you have some odd-ball custom drive flanges or spools or other internal slotting work in your future or just have an extremely strong desire to learn how to do those things, it's not worth it.