Dual Stage Jet Pumps. Great for DEEP well, irrigation / sprinkler applications. Includes injector and pressure switch. For applications not needing the injector, see Series 3-2L Dual Stage pumps. Diffusers are 20% glass fiber filled Delrin (Acetal) Impellers are 20% glass filled Noryl with SS threaded insert. This can be a big benifit for lakes or water which is low pH (4.5) which will corrode brass impellers.