The factory rubber rear upper shock mount for the GD WRX/STI chassis is a big rubber mount.They wear out over time, can dry crack, even come apart completely. When these mounts are new they have a lot of slop and "slow down" damper reactions to vertical inputs in the shocks. We can fix all of that.
Vorshlag has been making spherical shock mounts for years, for a variety of chassis: Corvette, BMW, NA/NB Miata and more. These mounts specifically for the late-model Subaru WRX/STI are made in-house at Vorshlag and feature the same oversized spherical bearing found in the company's front camber plates. These shock mounts are big, beefy, and as strong as a tank. Removing the stock rubber top mounts and replacing them with spherical top mounts will drastically improve suspension articulation and movement.
Note that these upper mounts are designed to work with Racecomp and GTWORX-brand coilovers ONLY. They will NOT work with stock struts/springs, nor will they work with other-brand coilovers.