This part is included in regular orders for the IVM6000-LP.
The RDSA (Rubber Stem and Disk Assembly) replaces the standard one that comes with a compatible 6000 series indexing valve manufactured or sold by KRain, Zoeller, Orenco, American Manufacturing, Quanics and others. This video shows how simple it is to swap out. It contains the magnetic signal array required to allow the IVM to sense the disk position and monitor the valve.
The stem is dyed black so it is easy to distinguish from the default one which is white.