HANDMADE: Made of Zirconia materials. We managed to make the ring thinnest and the lightest which makes it the most comfortable to wear. WATERPROOF&NO CHARGING REQUIRED: No have to worry about staying without a key when the phone battery is dying. Rings are waterproof. No need to remove your ring while washing hands, taking shower, or swimming. : One ring works with multiple cars. The ring is compatible with for all Model 3 and Model Y vehicles. The ring has the same security level as key card. ACTIVATION&USE: Find the right sensor the B pillar under the driver side camera and touch your knuckle onto the B pillar (knocking position) and do not touch the ring directly to the car. Size: 8 circumference: 59mm Color: Black Material: zirconium oxide Package Contents: 1x Smart Ring Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.