Make sure you look under the MBs when they arrive for the slider, you could miss them. They are wrapped in plastic.
There are two advantages that I can think of:
1. Some cast members will remind you of your DVC discount if they see it on your band.
2. If you place it over the clasp area it will keep the Magic Band from becoming unclasped.
It serves no other purpose other than decorative.
seriously feeling like a leper,,,,2 sets of MB's and no sliders.