Help your kids do things more efficiently and develop a strong sense of time. Also can be used as home office decoration. Great Gift for children and friends! Glass will be fragile under a sharp blow, carefully placed.2. As the timer can not replace mechanical clock, please allow 10% deviation.3. The sand is powdery. Please allow it get stuck or adsorbed on the glass. Just leave it to dry in the sun or shack it.4. Under adult supervision when little child under 3 years old use the timers - Item contains glass.