Tinksky Unique Luminous Glow in the Dark Cobblestone Man-made Pebbles Stone - 100 pcs/set (Blue) 100 pieces of the man-made pebbles in one set will be sold together. Color: blue (glow in the dark). Material: resin and photoluminescent pigment. Line a walkway, edge a flower bed or fill a planter with these unique acrylic pebbles Glow lasts approximately two to three hours after full sun exposure.