This knob is 3D printed from black PLA.  The knob has a brass insert for durability and an 8-32 set screw.  The paddle is laser cut from mahogany.  They are meant to fit a newer (post WW-II) Vibroplex.  The hole spacing is 7/16 inch, and the edge hole is sized to pass a 6-32 screw, while the inner one is sized to a close fit for an 8-32 screw.  These could fit Iambic Vibroplex products or even homebrew keys/keyers.  Shown in the photos is what the knob and paddle looks like on a Champion.  The key is not included in the sale, of course.  The top of the knob is textured.  I have a few other sets for sale right now.  Email me if you have any questions and thanks for looking!