This Danner impeller is a replacement for the Mag 18 magnetic drive pump. It is the part that moves the water, so swapping in a new one is the fix when the old impeller wears out.
Brand: Danner
Made for the Mag 18 pump
Impeller unit for the Mag Drive 18 Model B
Replace the impeller only with the pump unplugged, and rinse the housing before you install the new part.