I just copped some a month or so ago for my 4k.
Before you go getting all excited, they are a good upgrade, but at first you won't be able to notice a big difference. My reasoning behind saying that is this... Fad Pad w/ the corx installed gave my unit a stiffer pad feel. I was expecting them to be kinda "squishy" if you will.
They are about the same density as the OG pads. But if you are doing any velocity trickery, that is where you will see benefit. Catching the lower velocity strikes were a bit of a chore before Fat Pads but they have made it easier.
I will warn you now IF you buy the Fat Pads, they will come with a set of Corx. USE THEM! Apply them immediately! I tried the Fat Pad without Corx and almost broke a finger.
High! How are you?!