The guys on BBC website could probably be able to tell you were to get you the right one for your unit. I really wish Garmin would make the older software available, they still say they cant, I don't buy it. I would email you the zip file that someone sent me if you had an Echomap unit. I was not comfortable doing the rollback. You had to download the zip files to your computer, then unzip them and extract the Garmin file with the right files to a mico sd card, insert the card in your unit, turn on your unit while holding down the number 4 button. I'm not encouraging anyone to do this, I would hate to see anyone mess up their unit. Those of us that have done this are glad it worked!