Thank you for viewing. Product features: It accurately measures heart rate and heart rate variability 24/7 using green light and infrared LEDs, and it links with an app for immediate confirmation. I used it for about 3 months while sleeping, and I am selling it because I purchased another smart ring. As you can see in the images, it is in good condition with no noticeable scratches or stains, but please purchase only if you understand that it is a used item that has been handled by someone else. ○ Included accessories: All items included at the time of purchase. Box set (including instruction manual) Charging dock USB-C charging cable (unused) Trial ring set