Classic Equine's Saddle Shims are a tapered wedge closed cell foam that is used to fill the small gap or space behind the horses shoulder and under the front of the saddle. Shims are recommended in order to support, adjust for a better fit, or promote a more level fit. Place shims just under the front of the saddle and on top of the saddle pad as needed. Package of two.
Check out this video of Sherry Cervi explaining saddle fit & when & how to use saddle shims.
https://www.youtube.com/watch?v=l4iVhzeegyk