I received a Zojirushi’s stainless mug in exchange for my use and honest review.  The proprietary double-wall stainless steel vacuum insulation keeps drinks cold or hot for hours - the lid is leak proof and it is ergonomically designed to be easy to hold and carry.  The instruction booklet that came with it quite frankly was a little intimidating and I had to read it over several times to make sure I completely familiarized myself with its features and functionality.