... Double-walled c)directly from factory. Products Details DescriptionNameBorocilicate Heat-resistance Glass Tea Cup(Super clear), 50ml(cc)Item Code ... WCG-007DescriptionMouth-blown, heat-resistand glass tea cup. By using the new technique ... borosilicate glass, it is light & thin, but durable and heat-resistant, which is unlike the traiditonal common glass. Dishwasher safe ...