Just received this set today and I gotta say I'm really glad I decided to get it. The overall quality of this set is really good with nice tight joints, thick plastic and a great color match. The add-on features ball joints at the hip and swivel joints at the knee. You don't have to modify anything on your Devastator to use this set, however if you want you can unscrew the missiles from the original hip accesory and attach them to his new upper legs. The only slight downside I found is it can be difficult to get Devastator to stand up. His legs are a bit too far forward making it a bit tricky to pose him without additional support. If you bend his knees backwards slightly though he'll stand nicely. For looks I totally recommend the set though! Adds some extra height and improves the overall proportions.