Note: sometimes we may run out of these aluminum shims, in that cse we may send the steel 4 degree shims. They work the same.
If you have lifted the rear of your 2005+ Xterra and have a slight vibration between 35-45mph you may need these. We have 3 degree billet aluminum shims specially designed for the Xterra's rear leaf springs. These are billet so they will not crack or rust. They are also as short as possible to conform to the arch of the spring and as thin as possible to decrease the amount of ride height loss (about 1/8" some other generic shims can loose 3/8" of height). Price is for the pair (including new center pins). 
Installation is pretty easy'
-jack up vehicle and support with jack stands
-loosen u bolts on one side
-clamp springs with c-clamp and remove center pin
-install shims and new pin (thick end of the shim goes FORWARD, unlike most other vehicle shims)
-cut off excess bolt
-lower axle and tighten u-bolts
-do other side