The inserts that were all separate are for the wild child. I never bought the actual HH insert because I had bought a bunch of the microfibre inserts. Then when I got the GKs I just used one of them because they're better.

And yes. The long bit just folds over itself for extra absorption. Depending on how much he wees though, you might be able to get away without the booster in the WC. Give it a go. Don't do what I did and forget the cover for it though - very unhappy girl the next morning and a very, very wet cot!!