Four Basic Models There are four different models based on the same Model A construction. Each covers a specific flow and pressure range. If possible, choose a model you will use in the upper range of its flow rate capacity. For a listing of Model A pumps which run off 230VAC, click on Model A 230VAC. Three Materials of Construction Most Model A pumps are available using three different materials of construction; type 316 stainless steel, CTFE, and PEEK.