I am using similac r.s which is added rice starch. It is thicker than regular formula but not too thick. I am using playtex drop-ins bottles and none of the nipples work with this formula. If I use rapid it is too fast, slow and medium nothing comes out and the y cut is too fast. When I try to widen the slow I can’t get it right (usually end up too big) any suggestions on other bottles maybe too help?