Stainless steel vacuum insulation keeps beverages hot or cold for hours; Heat retention: 187°F @ 1 hr. / 151°F @ 6 hrs. ; Cold Retention: 48°F @ 6 hrs. Designed to drink directly out of the mug; Rounded sip area Easy-to-clean nonstick coated interior A special manufacturing technique was used to make the body ultra-lightweight and compact 1-5/8” (4cm) wide mouth opening accommodates full-size ice cubes, and is easy to fill