Dual-Layer Tumbler 570ml - White/GreenTwo cups in one. The Dual Layer Tumbler pairs a 570ml high borosilicate glass inner cup with a 600ml 316 stainless steel outer, giving you the clarity of glass for brewing tea or coffee and the insulation of steel for keeping it at temperature. Use them together or pull them apart for two separate vessels. The glass inner is perfect for watching leaves unfurl or colours bloom, while the steel outer handles the heavy lifting with up to 6 hours of heat