This is a direct replacement to the vehicles original air conditioning fan.
Air-con not working on your Defender as it should?
It's probably down to a seized or worn-out condenser fan, the OEM fan was never up to the job, no water seal on the motor, bushes rather than ball bearings.
Revotec have put together to retrofit fan kit that simply bolts in place of the original, with a long life and water sealed motor. This is the fan they should have fitted from new.