Not effective or fit for purpose.
The fans produce barely any air flow, they are either seriously underpowered or their enclosure is poorly designed as to trap the air.
No observed change in core temperatures when compared against propping the back of my laptop up off the table with a pencil laid flat to allow easier air intake from the underside vents.
I presume any reported improvments by others are purely because of this versus any effect of the fans. I will return it and continue to use the pencil instead.