This is a head/neck/face replacement kit for FansToys FT-16T Sovereign aka Galvatron, to make him look like his Marvel comics appearance as drawn by Geoff Senior. The head and neck are three parts: The neck, the core block, and the helmet, and four faces are included: Neutral, Anger, Yell, and Laugh. Faces are installed by inserting them into the core block and then fitting the helmet down over the assembly.
This kit is installed on the figure midway through the torso transformation by removing a single screw from the back of the collar, underneath the purple back column. A gentle pull should separate the two halves, and from there it's just a swap and reassembly. This kit is 100% transformable with the figure and does not need to be removed.