Yoyorule 100 Pcs Glow in The Dark Stones Pebbles Rock for Fish Tank Aquarium Material:Plastic. Quantity: 100. The size of 1 pc Pebble:1.7cm x 2.4cm/0.67'' x 0.94''(approx) Line a walkway, edge a flower bed or decor garden ,fish tank with these unique pebbles. Glow lasts approximately two to three hours after full sun exposure After being exposed to strong daylight with 3 hours, these pebbles can be lighted within 1-2 hours in the dark.