SNOW HOME Double Glass Double Walled Glass Mug 250 ml Home Office Cup Double Layer Thermal Insulated Glass Cup with Handle 1 Piece Thermal Insulated Borosilicate Glass Cup The product has double layer glass and thermisil properties. Heat resistant - Stylish - Elegant and Double Walled Design. Made from high quality borosilicate glass. Don't let your coffee get cold at home, at work or in the office. 250 ml Borosilicate Glass It has a granite-like structure - It is very difficult to wear - It does not scratch - It is resistant to high temperatures and is also resistant to low temperatures. There is a round mark on the bottom of the glass due to the construction of the double-walled glass. It's not a defect!!? We recommend hand washing.