The combination of BPA-free, EU food-grade silicone rubber and 304 stainless steel makes the Detour Collapsible Mug the epitomy of packable and durable. The Cool-Grip fins molded into the side walls protect you from hot or cold for a more comfortable grip and it collapses down to a fraction of it's original size for nesting and storage. When space is at a premium, this is the premium 475ml mug you want.