Hydration meets backpack-proof engineering in the Ello® Oasis 18oz Insulated Stainless Steel Kids Tumbler, a double-walled vacuum-insulated tumbler with an innovative retracting Hide-A-Straw lid, leak-proof seal, BPA-free construction, and a cupholder-friendly silhouette that keeps drinks cold for up to 18 hours from the classroom to the soccer field.