The AC on my 2002 Chevy Cavalier stopped blowing cold in the fall and I had planned on getting it checked out and recharged once the AC check specials started.  I saw this for $30 and it seems too good to be true.  Do they work?  Anything I should look out for?

![enter image description here][1]


  [1]: https://i.sstatic.net/PZhts.jpg