Product Information Material: TPR Size:6cm When sticky small balls absorb some light, they will glow in the dark. If the light from the luminous ball is very weak, please place the viscous ball in a place with a light source, such as sunlight or strong light, and the viscous ball absorbs it for 3-5 minutes. You can put these ceiling balls on a clean and flat surface, such as walls, ceilings, etc., wait for the luminous balls to fall slowly, and then grab them. Please note that sticky balls cannot work on smooth surfaces. Package included: 4PCS Sticky Balls Note Please allow 2-3 cm difference due to manual measurement. Besides different computers display colors differently, the color of the actual item may vary slightly from the below images, thanks for your understanding(1 inch = 2.54 cm)