You clearly show a see through net bag with five wooden capsules in it. You invite four volunteers and ask them to pick any capsule. You keep the last capsule. When the volunteers open the capsule they find it empty or find some worthless trinket in it. When you open your capsule you find a gold ring or some precious item in it. Everything is self-contained and automatic no sleights of hand or palming or switching.
The capsules are made of wood and are lacquered to a high finish.