I use this in my "old as dirt" DX3R Pro, and also installed one in my friend's DX5? (Not sure model). Removed AA battery tray, cut wires going to battery tray, soldered on servo plug to plug into the plug on the battery, and velcroed the new battery in. Lasts a LONG time on a charge, has a little higher voltage which "seemed" to make the radio feel more connected/responsive, and is pretty light. LIFE packs are far more stable and safe than lipo options as well.