Base Plates have two bearing discs with a corresponding circle of holes for SPEAR or Tongs rods. The discs are welded to a central ltube. At the bottom end there is a suspension disc fitting to your planetary shank, at the upper end there is a flat spring adding pressure to the rods for better electrical contact and more smooth rotation.
Base plates are usually made for rods 250mm or 300mm long, but can be ordereed in any other length as well. When chosing the height keep in mind that short rods come with lower capacity (because both ends cannot carry products) but long (thin) rods have less stabiltiy.
Chose a Base Plate which fits to your planetary axle. The position and number of the holes should fit to the gears size of your rods. Holes in the bearing plates of the Base Plate should never remain empty during the coating process.