Q: What are these endlinks made of, and will they rattle?

They use forged aluminum and steel construction with sealed, Teflon-lined spherical sockets. That sealed spherical design stays quiet and smooth while handling the higher loads of aggressive sway bars, big wheels and tires, and rough terrain. You get the precision of motorsport-style hardware without the squeaks, clunks, or constant maintenance that usually come with exposed spherical joints, which matters when the car is also a daily driver.