Single letter size ： about 3.2cm x3 cm
The main raw material of luminous sticker is a optical energy storage luminous powder, which stored optical energy after phosphor powder was irradiated by natural light, fluorescent light, ultraviolet light. When stopped light irradiation, it released slowly in the form of fluorescence. So at night or in the dark, we can still see the luminous and the time it lasted is between several hours to more than ten hours. So try to expose it outside to absorb light as much as possible after receiving the goods and do not shelter or cover it with something. It needs lighting to be luminous, and it will be brighter and last longer when absorb more light.