Product review (5 stars): Tip to a tough install, Good product
If you're not mechanically inclined you may have a tough time getting the retaining spring in on the drum side. For me the special tools provided did not hold the ring in place with enough force to keep it there, so it kept pulling out.  What I had to do was slightly overstretch the spring by holding the wire down with my feet and pulling up on it, just don't do it so much that it won't keep a good seal afterwards. After I did that it went on first try and it hasn't leaked yet.  Good luck hope this helps.