Porsche Becker CDR-220 Radio Replacement Knobs 3D Printed Parts. 3D printed with high quality Black PETG which is a hard heat resistant plastic ideal for use in vehicles, unlike others sold . They will also not get sticky like the rubberised originals. Depending on the age and condition of the of the head unit a small amount of glue maybe need for permanent fitment. Included is X2 Knobs Any questions please ask. Please note, these items are 3D printed (not injection moulded) 3D printing works by building up very thin layers of plastic. Which this in mind some layer lines will be visible. Every care will be taken to provide the best quality and strength. If you have any questions about the finish or process please feel free to ask.