About this item When you receive the parcel please kindly put all the gravels in the sun for about half an hour to make them charge fully for the first time use, then you can watch in the dark, they will glow brightly. They will last the glowing for about 2 -3 hours in the fully dark space. They can charge and glow repeatedly. If you want it to glow all the time in the dark indoor or outdoor please install a LED UV black light above them. It can be applied to indoor and outdoor flooring, to make the terrazzo, to decorate pool, bar, vase, fish tank and Aquarium, It can also be used to decorate the garden flower pots, to mark paths and walk way or as a border for plant beds or ponds. It varies in size. It includes about 280g in one PVC jar. It’s EN71 approved: non-toxic, non-radioactive and completely harmless to aquatic life.