臂，扭力彈簧

Installed this as a direct replacement for the standard torsion spring arm and it matched the original specs exactly. The metal feels sturdy and there's no wobble in the head support now.

The torsion spring arm fit perfectly onto the head mechanism with zero fiddling, and the metal feels reassuringly solid compared to the flimsy original. It’s holding tension exactly as it should after a week of daily use, so I’m glad I went with this replacement rather than trying to rig something c

Bought this to replace a worn torsion spring on my head support mechanism and it clicked right into place without any modification. The standard option turned out to be exactly the right stiffness for my setup, and it's held up through weeks of daily use without sagging.