A ballistic helmet would prevent player from getting instakilled by MTF headshots if he faces them backwards or from the side. Ballistic vest can protect only torso and the only effect is reduced damage while a ballistic helmet would prevent instant death to head. The side effect is shaky screen. No bloodloss occurs as a result and only injuries are applied. The helmet can be worn at the same time as night vision goggles under condition that goggles got equipped first.

Another side effect of the helmet would be vision being yellow due to the helmet's glass.

SCP-914 refining:

Rough- Item gets destroyed. If it was composed with SCP-148, SCP-148's ingot will show up.

Coarse- Item gets destroyed but if it got composed with SCP-148. It will return to it's normal, undamaged state with SCP-148 aside.

1:1- Ballistic vest or vice versa if ballistic vest is put inside. Same with other variants of those items.

Fine- Helmet will protect from the screen going shaky in case of headshots and damage will be even more reduced but mouse sensivity would get passively lowered (multiplied by 0.8) just for wearing it. Yellow goggles of the helmet would get expanded and protect from frontal headshots but damaged glass would weaken visibility. With SCP-148 the helmet protects from the same memetic effects as heavy gas mask does. Putting the helmet with damaged glass on "fine" results in glass being fixed.

Very Fine- The helmet would turn out to be so heavy that wearing it would cause injury meter to quickly rise and eventually result in neck being snapped as well as mouse sensivity would go crazy. Can also be composed with SCP-148 but that wouldn't help much.