Years ago they had something called a Poly Patch, basically a (Shuuuddeeeerr) sabot for rd balls. At the time i was fairly new to muzzleloading and tried some. They worked ok, but a think you will get better accuracy, and be safer, with a cloth patch. There was a chance for the ball to come loose with those things and possibly cause a barrel obstruction if it didn't roll out of the barrel. That and they were not a real tight fit, so there was a chance for the Poly Patch and ball to move forward off the charge. Not a good situation. Stick with the stuff that has workd for a few hundred years and you can't go wrong.