During a period of about 3 years I've purchased four different types of these double walled glass mugs for coffee. Living alone I make one cup of coffee at a time and prefer to prepare a large one of 10-12 ounces and want it to remain hot as long as possible. That is my number one priority. Secondly is durability. This is by far the best of these I've owned. It is heavier glass and has a wooden top with a synthetic seal around the edge instead of single walled glass. It doesn't rattle and sweat and release heat the way the others I've purchased have. Also it is very sturdy. The others have been much more fragile. The best of the lot has shattered twice. Once when the handle caused a crack which fractured the whole cup and the other when my dog bump it off on the carpet from the arm of my chair. Another one had a shattered lid when it arrived despite careful packaging.In short this one has all features I want at a cheaper price than the previously best of the lot. It seems to be thicker with a larger dead space between the walls because it retains heat longer as well!! However this means it isn't really a 16 ounce cup. It isn't even a 12 ounce in practice. 10 is about the safest amount if the lid is to be used.