If you own NTG4 (specifically pre-facelift 204, as in my case), you want authentic MB DVDs; the most recent update was released in 2019. Therefore, search eBay for NTG4-204 DVDs (do not confuse with NTG4-212, as they are distinct). However, if your 204 is a facelift model (if I recall correctly, model year 2011 and newer), it is likely equipped with NTG4.5, which requires a PIN unique to your VIN, along with the corresponding DVDs. Both may be acquired from Mercedes-Benz or select independent dealers such as Comandonline in Lightwater, Surrey (forum sponsors!). Utilize a free online VIN decoder to ascertain the version of your Comand system associated with your VIN. Avoid counterfeit DVDs, since they may damage your Comand system—costly repercussions!