In a number of recipes, I see Diamond Crystal recommended as the kosher salt to use. Where I live, only Morton's is available. Is there some superior quality to Diamond Crystal kosher salt that I might not get out of another brand? 
Many recipes specify salt measurements by volume, but different brands of salt vary by density. In order to consistently predict the weight of salt used, recipe authors fix the density by fixing the brand. If you want to know whether you can use the brand that's available to you, the answer is yes. You just need to convert the units to weight. From Simply Recipes:  By weight, the brands are the same and can be used interchangeably. This is why you should ideally always measure large amounts of kosher salt by weight to be precise. But if you’re measuring by volume — or if a recipe only lists the kosher salt by volume — you can run into issues. Since Morton kosher salt is has a finer grind, you’ll pack more into a cup than if you’re using Diamond Crystal. This can really throw off a recipe! First off, look for (or ask!) which brand of kosher salt is recommended in the recipe, especially if the recipe calls for larger amounts of salt. (If you only need a teaspoon or so, you're usually ok using either brand without throwing off the recipe that much.) Then either use the brand specified, or follow this conversion chart:  1 cup of Morton’s Kosher Salt = 241 grams = 1 3/4 cup minus 1 teaspoon of Diamond Crystal Kosher Salt  1 cup of Diamond Crystal Kosher Salt = 137 grams = 1/2 cup plus 2 teaspoons of Morton’s Kosher Salt    137/241 is approximately 0.568, or a bit more than half. If you need to be precise, measure by weight. 