Estimated Value: 6,000 gp
While wearing this ring, you can use an action to speak its command word. When you do so, you can see into and through solid matter for 1 minute. This vision has a radius of 30 feet. To you, solid objects within that radius appear transparent and don't prevent light from passing through them. The vision can penetrate 1 foot of stone, 1 inch of common metal, or up to 3 feet of wood or dirt. Thicker substances block the vision, as does a thin sheet of lead.
Whenever you use the ring again before taking a long rest, you must succeed on a DC 15 Constitution saving throw or gain one level of exhaustion.
Source: DMG p193