the arm socket is made of 4 components:
1) Arm socket (with a nut)
2) Arm holder
3) Arm torque bush
4) Arm cap
The Arm torque bush is a small black plastic cylinder located under the cap
that fit with the arm socket. Its use is for keep the arm firmly on the
socket and for prevent "squeacking" noise because of metal parts stroke.
This torque bush is not fixed under the cap and it's removable and changeble.
So don't be afraid! The only thing to do is to place the torque bush on
the socket arm and then close it with the cap.
picture can help you. You only have
to pay attention with the orientation of the bush. The small bump need to
be up for right fit of the cap and the arm.
Hope this was helpful for you.