Tumbler, with slide-open lid, 530 ml (18 oz) S'well Tumblers feature Therma-S'well™ technology - a triple-layered, vacuum-insulated construction made of high quality, 18/8, food-grade stainless steel walls plus a copper wall layer for superior temperature retention. It means that beverages will stay cold for up to 17 hours and hot for up to 4, while maintaining a condensation-free exterior. The 530 ml (18oz) tumblers are perfect for on-the-go drinking, featuring a slide-open lid meant to create a splash-proof experience. BPA and BPS Free. Hand-wash only. By choosing re-usable S'well bottles you can help reduce the use of single-use plastic products that pose a threat to our environment.