Yeah, it is without the centre part. I don't see any reason to use the centre part because it makes the new holder look almost like the stock holder. There are a few tricky parts assembling the holder together. The trickiest part in my opinion was removing the small spring that holds the seat's...
It is basically the easiest one to attach to the bike because it is 100% plug and play. It comes with great instructions, you can't go wrong with it.
This is the end result: