Charging dock is size-specific and can only be used with the matching Oura ring size (ring sold separately) Oura ring can take between 20-80 minutes to charge, depending on the current battery level. It’s important that your sleep ring be charged to at least 30% before going to bed. If your battery level isn't at least 30% prior to bed, you’ll miss out on your Sleep insights for the night After connecting your ring to the docking station, it will pulse white while your ring is charging, making it easy to see when your ring has a proper connection Charging dock LED will light up green when your ring is fully charged, so you can easily tell when it's ready for use Included USB charging power cord is meant to be supplied by an external 5Vdc supply that complies with IEC 62368-1 standard