In the US and Canada, the standard mason jar opening comes in two sizes: regular (2 and 3/8 inches wide) and wide mouth (3 inches wide). The wide mouth jar is generally a better choice for salads because it’s much easier to get ingredients in and out of the wider opening. Mason jars come in a variety of sizes, but the ones most commonly used for salad recipes are the pint (16 oz) and quart (32oz) size jars. I've used the 16 oz size mason jars for the recipes pictured.