The high amount of carbon fibers makes ... of the XT family. PETG filaments generally show a very low tendency to deform during printing, and with the high fiber content of the XT-CF20, the ...

[Nerd] shows how the ruby nozzle could print PLA after printing with carbon fiber filament with no ill effects.The nozzles fit like a common E3D nozzle, so they’ll go on a lot of printers.

This is a version of the K1 meant to print carbon fiber filament, and it has a trimetal hotend that doesn't use the little plastic pipe, but metal all the way through from the extruder to the nozzle.