This intermediate ring serves as an adapter. It clicks into place between the two halves and enables a larger reel width. The standard reels end at 56 mm. These rings allow you to widen the reel by intervals of 16 mm.

For example, from 56 mm to 72 mm with one core, from 56 mm to 88 mm with two cores, etc. These cores come in two core diameters of 100 mm and 152 mm.