i play the 'old' blue sponge national version of Rx9 in 39˚ and gone through at least 10-15 sheets on my forehand and can say that the QC of the topsheet and the overall thickness is really good, but the sponges aren't. they change in hardness but also in density, so it is quite hard to get the boosting right even if you are very careful. but in my opinion that isn't too bad for a rubber in that price range and only start to matter if you play more then 2-3 times a week or play more serious then hobby and need something reliable in important matches (but those people would anyway buy something else or are sponsored). i am fine with it and interested to see what the new Rx9 neo has to offer