Handmade, please allow almost no deviation. The interior consists of selected sea sand, the interior of glass and the exterior of solid plastic with double protection. A good timer that children can use to get a clear idea of cooking timing and time. An elegant gift for family and friends. Since the hourglass does not match the clock exactly, please allow an error of 10%. It has a good seal, but air sometimes gets in. If the sand gets stuck, the timer just needs to stay in the sun for a while. Since the hourglass does not match the clock exactly, please allow an error of 10%. It has a good seal, but air sometimes enters it. If the sand gets stuck, the timer just needs to stay in the sun for a while.