Constructed with double wall & 18/8 food grade stainless steel, fully-rugged and won't rust. Vacuum insulation for maximum temperature retention, keeping drinks hot/cold for as long as 12 hrs. Hygienic,insulated, locking lid, doubles as a cup, very simple and lovely shape. BPA-free,leakproof, condensation proof, insulated, thermal, twist off lid, stain-resistant. Moderate capacity, small size, convenient to carry; really cute design, and variety of colors available.