When Noctua 40mm is your only friends and options : r/sffpc
I wanted to upgrade my stock part cooling fan to a pair of noctua 40mm fans and when I did a test run they barely push any air through the ducts compared
Noctua NF-A4x10 FLX 40mm Case fans Quiet Cooling Fan 5V 12V PWM Intelligent Temperature Control Chassis Radiator Cooler Fan - AliExpress
Velocity stack for Noctua 40mm fan NF-A4x10 by cmh | Download free STL model | Printables.com
Installing Noctua 40mm fans in my router
GameCube 40mm Screwless fan adapter by Retro Frog | Download free STL model | Printables.com
GameCube 3D Printable 40mm fan adapter available to download | RetroRGB