The MK10 extruders on all our Flashforge Creator Pro printers do not grip flex filament well enough to consistently push it through without slippage resulting in failed prints. These metal extruder lever setups solve the problem nicely - gripping the filament much tighter.
Installing them can be tricky though. The supplied M3 bolt for the idler wheel is about 1mm too long and needs to be shaved off (or buy a shorter bolt). They supply a washer to go on top, but the washer interferes with the rotation of the idler wheel.
With that slight modification it is a nicely made piece of equipment and all of our Flashforge printers can now use Ninjaflex TPU filament.