If you have the original D-Tek FuZion, make sure you buy the Pro Mount kit and the Nozzle kit, and use the appropriate nozzle for your system.
Be aware that the original FuZion came bowed.
Version Two of the FuZion comes flat and with the extra O-rings. If you are performance-minded, make sure you select one of the two o-rngs to manually bowed. Be advised that bowing is a one-way street. Once bowed, you cannot go back to flat.
No matter, the flat block wouldn't hold a candle against the nbowed block because it exerts extra pressure on the cores.
The jury is still out whether this is the new kingpin or the title is still maintained by the EK Supreme. Aigomorla will tell you that the restriction of the EK Supreme brings performance benefits.
If you don't much care about getting that last degree of thermal capability, then by all means use this Version Two block as is. I still highly recommend that you bow this block.
Further guidance upon request.
Ian