Lime juice is a common ingredient for many cocktails. While a relatively simple product, it can be a stumbling block for many beginners. The important thing to know, is that when a recipe calls for "lime juice", it should always be freshly squeezed and not from a bottle. It is easy to initially think that there is nothing wrong with those little plastic limes you might see in the grocery store, but it really isn't the same thing. Worse, is to think "Rose's Lime Juice" (or any type of "Sour Mix") is a proper substitute. Another problem wth lime juice in cocktails, are the recipes which simply call for "juice of half a lime", this is NEVER an appropriate ingredient description. The amount of juice from one lime to the next, could easily vary by half an ounce or more. Lime juice is a very potent ingredient, and this much difference will be a disaster in the final product.