Example
Fan 4012 = 40x40x12mm, Fan 4020= 40x40x20mm, Fan 6010 = 60x60x10mm, Fan 12040 = 120x120x40mm…
the second source of error in choosing fans is the type of connectors…
Passive case means use without a fan.
You will have to choose,
it will be either the passiv case or the radiator + Fan,
but I don’t think you can do both unless you have something to proven.