The definition of 4 dashes = 1.25 ml has the advantage of making the common "2 dashes" specification equal to 1/8 tsp, which is a common measuring spoon found in most people's kitchens. And b.t.w., the Easy Jigger (mine came courtesy of Santa) is now my favorite cocktail jigger (despite its industrial appearance) since it has a 2 oz capacity and many, many increments, down to very small amounts, in both ml and oz. I always wash it by hand and the markings are holding up well.

I measured the volume of 4 dashes to arrive at my dash equivalent. Many thanks for buying a jogger. Rine between uses and put in your dishwasher every week or other week, depending on the frequency of use.