What is stacking ring?
It is always in conjunction with Hub Printable disk. It refers to the small ridge around the inner plastic center ring on the disk. Its purpose is to keep the disks slightly separated when stacked on a spindle. Stacking ring is usually present on a standard disk. When a disk is to be hub printable, there is no stacking ring so that the printable surface can be applied all the way to the center hub. Also, for disks that are to be thermal printed, there is an advantage to not having a stacking ring. The stacking ring sticks up and interferes with the thermal printer head. A thermal printer cannot print any closer than 1/4″ or so from the stacking ring. When there is no stacking ring there is no restriction on the thermal printing area.
