Safety Hourglass Timer: The 30-minute sand timer made by friendly high borosilicate glass and acrylic material. And each hour glass has a digital time mark. easy to distinguish which timer for which usage Non-breakable Design: The outer layer is made of hard acrylic material and the inner one is made of glasswhich is protected by double layer. Besides, the silver textured top caps are firm & durable, so it will not easily cut your children's hands Best Time Management Tool: The large hour glasses with sand 30minutes help your kids do things more efficiently and develop a strong sense of time. The hourglass timer 30 minute can be used for cooking, games, classroom, study, desk office decorative and teachers use Notice: This hourglass sand timer is mainly made for games, which is not a precision timing device, so there is time deviation. But SuLiao kids hourglass timer has achieved the highest quality 5% industry standard in the USA