Plate for the underside of your Neptune 3 plus (probably 4 plus as well) to mount a BTT Octopus to. Will need to dremel/remove two of the old motherboard studs, one of the cover studs, and a tie-down point. Fairly easy process but be careful and take it slow as the stud are actually seem pressed through the base sheet metal and not fully welded. So you may end up with slight imperfections topside of the unit if the two pieces separate while dremeling. (see pic) Fan must also be moved to other side of plate, cooling performance is still sufficient for default setup but if expanded a new solution may be needed.