Glow-in-the-dark pebbles mark a path or highlight a flower bed! The 100-piece set can line a walkway, edge a flower bed or fill a planter with unique acrylic pebbles. After being exposed to daylight, these pebbles glow in the dark! Glow lasts approximately 3-5 hours after full sun exposure. The pebbles are flat, marble size and made of a poly resin material.