The sensor has "Mounting threads: 4x M3, rectangularly arranged at intervals 35 x 44 mm". Is the idea, if you are going to use those, to drill holes in my case to mount it, or is there some sort of adapter plate to mount to a 120mm or 140mm fan or rad or similar?
You do not need to use all 4 holes to mount the device... 1 would be sufficient.
And if you have one of the port's
(fittings) directly connected to a radiator or block, etc., you really do not need to use the mounting holes at all.