Specification: 100% Brand and high quality Material : resin + Photoluminescent pigment Diameter: approx. 20-30mm / 0.8-1.2 inches Quantity: About 50pcs Feature: Luminous pebble stones. The pebbles need enough sunlight to absorb ultraviolet light before they can glow in the dark. Convenient to use. Can be used to decorate walkway, lawns and gardens, aquariums, and swimming pools. Can be used to decorate potted plants, gardening. How do you make them glow? 1.Don't leave the pebbles under light with the package . 2.Don't pile up pebbles , make sure each pebble is fully illuminated . 3.When the pebbles are glowing , please make sure the surroundings are dark enough . 4.You can enjoy the glowing pebbles,the longer the absorption time , the longer the illumination time . Package included:50pcs Pebble Stones Note: Please allow 1-3mm errors due to manual measurement. Item color displayed in photos may be showing slightly different on your computer monitor since monitors are not calibrated same.