The Ultra ThinLine Western Felt Liner is made of the highest quality feltand isdesigned to be lightweight yet durable enough for everyday use. Panels of the Ultra ThinLine (3/16") performance foam are sewn on either side of the 6mm blended felt pad spine, creating a spine free channel and wither profile to accommodate varying wither types. At the bottom of each panel is an opening to allow for the use of shims to make minor saddle fitting adjustments. Shims (sold separately) should be used only as needed. Proven the most effective saddle pad for increased communication between horse and rider, Ultra ThinLine pads provide the following benefits: Makes it easier to sit and ride the gaits while giving an ultimate close contact feel. Keeps the rider's back stable and healthy by providing superior shock absorption--prevents sore backs Protects the horse's back and encourages proper rounding and movement Eliminates both pitch and yaw (both types of saddle slip) of the saddle Protects your show pad and your horse with this liner. For minor saddle-fitting adjustments, pair this pad with the ThinLine Shims ! Made in the USA.