This gasket protects the PTFE Tube where it passes through the case on the top backside.  I was worried that the PTFE Tube would begin to rub through on the sharp metal case edges.  This should prevent that completely.   I printed this in ASA at standard 0.02 layers.  It would be best if you print using ASA, ABS, or PETG, due to being slightly more flexible than PLA.  PLA may not want to snap into place as easily.  But you can try it as it only takes seconds to print.