There is a lot more to making your bow quiet than string silencing material. I have found that when everything else is wrong cat whiskers will help the most to make your bow quiet. They are easy to slide up and down to get the perfect spot, plus you can trim to size etc.
When everything else is perfect-brace height, nock height, nock tightness, arrow weight, string type and number of strands etc. it takes very little to get your set up quiet as that proverbial mouse. A little fur, yarn or rubber-they all work equally well at that point.