Does the neck on your T-800 droop forward, i.e cannot support it's own weight when the head is attached?
 
This clip pushes into the lower neck and removes the droop. It pushes in from the front. Keeping the neck tilted back, push in until you either hear a click, or the clip is out of sight. The neck will then be droop-free. It is fiddly, but satisfying once done!
 
Note - clip tab faces upwards.
 
Note - you will see the clip from the sides and maybe not the same appearance on each side, as how you push\fit this, will determine the outcome. See listing photos.
 
This does come in black, although you could paint silver before applying.
 
You'll receive 2 clips, as we know accidents happen. They are delicate, so care will be needed.