These shims are exactly what the doctor ordered to remedy that 30-40mph vibration in my Xterra. The vibration started when I added the Old Man Emu 2.5 lift kit.
Two things I would recommend, contrary to the above review:
1. I clamped the new leaf packs together and removed the center pin, running the pin through the shim (no drilling needed).
2. On the X, the thick part of the shim should be toward the FRONT (so the triangle points to the rear), lining up the rear diff more with the drive shaft.
They fit great and fixed the problem. (Oh and the team at All Dogs was quick to respond when I chatted to confirm placement. 5 Stars for service, too!)