This double sided merino wool liner is made with 100% merino wool fleece on synthetic backing. This liner is made with a velcro opening at the front edge for the included 1/4" thick liner insert.  
 
Please note that a "low" wither relief has almost zero spinal contour. 
 
You can use any saddle pad or liner under your bareback pad as long as it is smooth, especially along the spine, with no abrupt edges under your weight.