Essentially it's a 4.5mm rotor spacer and two 3mm axle spacers or they do one requires dishing ... I assume inhouse CNC cutters with prepreg, but maybe the industry is such that you can source ... @kcy4130: Probably steel.
Kogel Releases CNC-Machined Crankset Preload Adjuster ... It's like using a colored stem spacer or clamp-on grip ends. ... cranks and sold them to get eeWings I was super happy with getting a pre-load collar made of metal.