Shims are additions to saddles and are designed to change 
the shape of the saddle to accomplish several things:

1. Front to back leveling of the saddle, which can often be “downhill”
   
   
2. Shift the rider’s center of gravity further back on the horse and over its stronger and most active rear quarters
   
   
3. Add a flared shape to the front of the saddle, allowing freedom of the horses shoulder motion
   
   
4. In the case of extreme sway in the horse's back, a center shim can be added.

Shims are designed to be used in conjunction with Theraflex Saddle Pad which locates them in relation to the saddle with repeated accuracy.