Double-wall 16 oz Borosilicate Glass Coffee Mug Cup, set of 2 PERFECT CAPACITY : 16-Ounce , set of 2 ELABORATE DESIGN: Durable double layer construction remains cool and prevents condensation. SAFE WASHING: safe for dishwasher and microwave use; not for use with metal utensils. TOP QUALITY: made of lead-free borosilicate glass, its heat-resisting and brilliance. Absolutely no air bubble on the walls.(up to 520F ) WARM REMINDED: There is a small hole in the bottom of the cup, which is the unique trace of the manual blowing process.Not a flaw!