YETI Rambler 20oz Tumbler Stainless Steel The Rambler 20oz is made from durable stainless steel with double-wall vacuum insulation to protect your hot or cold beverages at all costs! FEATURES: 591ml / 20 US fl oz Double-wall vacuum insulation 18/8 Stainless Steel Size: 7 x 17.5 x 8.9 cm.