Mouthcaller is that a pad that goes on your shoulder and straps around your back. If it is what I'm thinking of it's a very thin pad that feels like it might have a thin layer of gel in it. Anyway the reason I bought the simms replacment pad is because a buddy of mine had a pad like the one you are talking about (or similar to it) and that thin little thing took all of the hurt out shooting 3 1/2's. Now with the simms pad I can pattern and shoot more than I use to because it doesn't leave my arm sore for a week.