The Pro Flow oil pump for Sportsters was developed by Zippers according to Buz Buzzellie's Sportster Performance Handbook. ¹⁾
Compact Cad/Cam design, made of 6061 aluminum, O-ring sealing throughout, modular construction and fits without engine or frame modifications.

These pumps are no longer in production. ²⁾ There were two versions, one 3 stage and one 4 stage.
The 3-stage uses a gerotor stage for scavenging the cam chest.
Below there is a spur gear set that scavenge the sump, and at the bottom there is another gerotor stage that feeds the engine.
They also have an extra suction port into the spur gear stage, that port is plugged with and 1/8 NPT.
That port can be used if someone for example wants to connect the pump via external plumbing to the sump.

The 4 stage pumps has an additional 4th stage, which can be used to various things. Draining the rocker boxes, draining a turbo or whatever the engine builder wants.

3 stage shown below:
Top, gerotor stage that scavanges the cam chest.
Below , spur gear stage that scavenges the sump.
Bottom, gerotor stage that feeds the engine.

Pro Flow multi-stage oil pump. 3)

REPLACEMENT PARTS FOR PRO-FLOW SPORTSTER TYPE OIL PUMPS 4)
721756	Rebuild kit	For Sportster type Pro-Flow pumps. Contains all clips, keys, pins and O-rings needed for complete reassembly of the Pro-Flow Sportster style oil pump.
721845	Pro-Flow Main body	With gerotor set.
721846	Pro-Flow Scavenge section	With spur gears.
721847	Pro-Flow Feed section	With gerotor set for ZPN 721184
721848	Pro-Flow Feed section	With gerotor set for ZPN 721183
721849	Auxiliary section	With gerotor set for ZPN 721184
721850	Pro-Flow Oil pump cover
721851	Pro-Flow Drive shaft	Only for ZPN 721183
721852	Pro-Flow Drive shaft	Only for ZPN 721184
722121	Dowel pins	For oil pump set ZPN 721183 and ZPN 721184
722069	Mounting bolts	For ZPN 721183
722139	Mounting bolts	For ZPN 721184