The black ones always seemed to break apart at the blades and would end up plugging something up. Since Ive swithched to the yellow ones, only one has stripped at the keyway knotch. I havnt used the blue ones yet.
I had nothing but problems with the black impellers. I have the reversible pumps and the black would always get stuck, but since switching to the yellow ones I've had absolutely no problem. They are suppose to contain some sort of lubricant in them??