warm and natural also has a scrim
scrims are not always plastic- in fact often are a fabric-like cheese cloth-either cotton or linen
it is just a netting for the fibers to be adhered to that keep the batting from pulling apart- making it possible to quilt further apart- batts without scrim generally need to be quilted quite densly- like every 2"-4"= and are best for hand quilting- batts with scrim are more difficult to hand quilt and are better suited to machine quilting- polyester and cotton batts can be found with scrim.