I wanted to use silent fans on a HP Proliant ML350 G9, and wanted to use some Arctic P8 PWM PST I had, so I printed these adapters to fit in the same cages the stock fans are inserted on.

There is two versions, full and splitted. Both work perfectly fine, but you can save quite some filament using the splitted version. It's 4 parts (they need to be mirrored, that's why there is 4).

Designed to keep the fan inside the insert with pressure thanks to the PLA slight flex. You will obviously need fan mount screws.