The ResMed 12v to 24v converters are not just 12v to 24v generic power converters. They are made for the ResMed CPAPs and only support one machine. There are 3 parts. The 12 to 24 volt brick portion that has a cable that plugs into the CPAP. The plug is a propritary 3 pin plug. The same plug as on the 120v AC to 24v DC brick. The other 2 parts for the 12v to 24v converter are cables. One cable that plugs into the brick and has battery clips. Another cable that plugs into the brick and has a male cigarette lighter plug.