Slide tags are not considered interchangeable on multiple collars. They are permanently paired with the collar they are installed on. (Our traditional hanging tags, in circle or heart-shaped options can be used on any collar at any time, though). Because our slide tags do not have open hooks and must be sewed into the collars before shipping, it would not be practical to remove the tag to use it on another collar unless you wanted to mail the original collar back to us for transfer onto a new collar you intend to order. (Note: If you did this, the original collar would no longer be usable). If you wish to re-use an existing slide tag purchased from us, on a new collar purchase, email us at help@madebycleo.com for instructions on how to do this.For tags that can be easily transferred to different collars, we recommend choosing any of our non-slide I.D. tags, available in a number of colors in heart & circle shapes.