Since the display of rear derailleurs was first introduced to BikeCAD, whether or not a bike would include a derailleur was determined by whether or not the rear dropout had a derailleur hanger. With recent developments in drivetrain technology, the absence of a derailleur hanger no longer means the bike doesn't include a derailleur. In BikeCAD version 20.0 there is now an include checkbox in the rear derailleur section which ultimately dictates whether or not a derailleur is used. If the design does not include a derailleur hanger, the derailleur will be mounted to the rear axle. As always, the actual display of the rear derailleur can be turned on and off with the eyeball icon.