27oz single wall stainless steel bottle The M8 is Mizu’s most popular product because it is the ideal size and weight whether using at home, in your car, or on any adventure. Note: Single Wall is so lightweight because there is no double wall to weigh it down. No double wall means no insulation, folks. Cold beverages only in this one. Note: This bottle comes with a loop cap; sport cap also fits and is available for purchase separately.