https://smartringhq.com/blog/smart-ring-buying-guide/ https://smartringhq.com/assets/b99f34fc-86b7-422f-95be-41b4295da686/titanium-smart-ring-with-visible-ppg-sensor-array-close-up-af8b650a.jpg Close-up of a titanium smart ring showing the inner sensor face that houses the photoplethysmography LEDs. https://smartringhq.com/home/ https://smartringhq.com/assets/b99f34fc-86b7-422f-95be-41b4295da686/black-smart-ring-with-visible-internal-circuitry-on-a-6dd726a6.jpg Black smart ring with visible internal circuitry on a textured concrete surface