That's a great question. The necklace is an alternative way to wear the UPRIGHT posture trainers without any adhesives, and it's sold separately. It's great if you plan to use the device outdoors and need a way to secure it, or just don't want to purchase consumables.
There are some people that have a clear preference for the adhesives, others prefer the necklace, and there are also people that use both intermittently. It's mostly depends on personal preferences. The necklace can be purchase either on Amazon or on uprightpose.com. If you have any further questions I invite you to reach out to our support team at email@example.com, the in-app chat or the website chat.
Your Upright team