I have 3 of this type of pad.  Two I bought from Dixie Midnight and a 3rd from a discount tack supply catalog. Two are midnight blue in color, one is black. Other than the color they are the same thing.

I use mine under a Navajo blanket. The two combined blankets seem to be enough padding and I've not had any sore backs. I use mine mostly to disperse the sweat and heat. Before I got them, my blankets after a 20 -30 mile ride would be soaking wet and seems to double in weight.  With the pads, my blankets stay dry and since they are not soaking up sweat, they don't gain any extra weight.

I have not had any problems with galling or saddle sores under the pads.

You can see the pad peeking out from under the rear of the saddle in this photo. I use them with lightweight Cordura saddles for my daughter or my heavy western saddle for me.