This is a very hard question to answer.
The part is designed to eliminate the washout height setting or angle phase of the cyclic. I believe it's referred to as the "integrated washout type FBL head".
It attaches on the shaft directly below the rotor head, then to the top of the cyclic which has arms to control pitch. It keeps the cyclic and blades in alignment and controls steadiness.
I understand some Heli's have it, and some don't.
I know the purpose of the part, but don't know if I am explaining it correctly. I know if your Heli had this part new, then you must keep it, or you will definetly have a disaster on your hands.
It works somewhat like your automotive suspension works keeping the wheels in a controlled position. Bad example, but the best way I know to explain it.
I have these parts on two of my Heli's, one being a 1/4 Scale. I know to watch them for any signs of wear. it's best to change them vs. the outcome if you don't. If there is any looseness or slop in the arm, replace it. There cheap, but definetly needed.
I welcome any comments, as I would like to understand the part more.
I hope this helps a little, Dennis.