These are just the Power Plates for the Power Plate system. If you already own a Bomber TD3 lower assembly (cants, E-rings, center disk, etc) then all you need are these to get going. The M8X16mm screws to mount the plates to the cant disk are included, and one set (2) Power Plates as shown below.
Click here to see information on Entire Power Plate System
Click here for a PDF of the instructions for the Power Plate System.