Bell & Gossett bronze impeller for B&G Series 90 pumps, model 90-33, size 1-1/2AA. Impeller diameter must be specified when ordered as this impeller is trimmable. Impeller diameter will be found on the pump's I.D. tag. Impellers are installed on the end of the pump shaft, which spins the impeller in turn pumping water, or other liquid, throughout your system.