Tuxton Home Mug, Dark Chocolate, Set of 4; Restaurant Grade Nonporous Virtrified China; Thermal Shock Tested Restaurant grade vitrified china - thermal shock tested, low permeability Tuxton Home products have been used and tested in restaurants Microwave, dishwasher, freezer, oven safe Passes ca prop 65 and all U.S FDA requirements for lead and cadmium exposure. Microwave, dishwasher, freezer, oven safe. Designed for heavy/ double duty use; Can go from freezer to oven to table