It helps if you put up a link, like this:
http://www.spacosupply.com/index.cfm?itid=195&id=itid&cid=7&scid=20&mc=3
And that's a ballast kit, not a full ballast. You still need the housing and probably the cord to go from the ballast to the light. Which reminds me, you'll also need a socket and...