Before ordering your Ultrahuman Ring Air, use this sizing kit to find your perfect fit Wear the ring sizer for a minimum of 24 hours to ensure accuracy Position the ring so that the engraved size number faces the palm of your hand Wear it on your index, middle, or ring finger for optimal comfort and advanced sleep tracking It should fit snugly and not rotate freely around your finger. A proper fit ensures high data accuracy and comfort The sizers are made of high-grade plastic, while the actual Ultrahuman Ring Air is made from space-grade titanium and coated with scratch-resistant tungsten carbide for durability and quality Ultrahuman ring sizes differ from standard ring sizes. Available in sizes five to 14