Insulator between the Strut and Vehicle Body.

STRUT MOUNT-REAR,LEFT Suspension Strut Mount

Fits Outback, WRX

Suspension Shock or Strut Mount
Strut mounts or strut bearings are often service with the strut assembly, and when they fail they can make a squeaking noise while turning or a metallic clunk noise when going over bumps. If your Subaru is noisier than usual on bumpy roads or under braking, you may need new strut mounts.