What is this tag on my water pump stating I cannot use a clutch fan or spacer?

Aluminum water pumps installed by BPE are not recommended for use with mechanical fan spacers or clutches. These place extreme stress on the water pump and can lead to pump breakage and extreme damage.

If your build requires a clutch fan or spacer, please swap water pump to a cast iron that can handle the stress. BluePrint Engines does not cover warranty or damage that occurs if a clutch fan or spacer is used with the supplied aluminum water pumps.