4 inch white acrylic plastic craft rings come 12 pieces per package. They are 5/16 inches thick. They are measured 4 inches base on the outer diameter. They are made of a solid hard plastic material. Call them: plastic rings, craft rings, plastic rings for crafts, acrylic rings, white rings. These plastic craft rings are a great general purpose item used for various projects. We carry these rings in 3, 4 and 5 inches.