The ARRI BAT-G attaches to the top of the ALEXA, ALEXA Plus, ALEXA Plus 4:3, ALEXA M body, ALEXA Studio, ALEXA HD, ALEXA HD Plus, ALEXA XT, ALEXA XT M body, ALEXA XT Plus or ALEXA XT Studio and accepts Gold mount on-board batteries. Batteries can be hot-swapped.