Twenty ounces. Made of stainless steel, double-layer vacuum insulation protects your hot or cold drinks at all costs. These standard lids are the only beverage lids that use magnets to lock your water, beer or favorite drinks. The cover adds a protective barrier to keep the beverage sealed and prevent heat or cold from escaping. Please note that the cover is not leak-proof and not prevent overflow. 20-ounce flat-bottomed cup, the size of the glass fits the standard-sized cup holder.