I have a 50mm pro alloy one on my Sapphire which I can't fault. Fit is really good and fans bolted straight on with no hassle.

Only problem I had when changing from the standard rad to an alloy one was that the fans never seemed to cut out once they had come on even when driving down the motorway. Apparently this is due to the alloy boss around the fan switch holding more heat, brought an uprated fan switch from MSD (cost about £18) and fans now cut in and out fine.