Pro tip: If you're in a restaurant or a coffee shop or any other place with a menu of products or services, you're more likely to get what you want if you use words that appear on the menu instead of trying to make stuff up (for example, if the sizes are called 8, 12, 16, and 20 ounce, asking for the "medium" is asking for trouble).

If you're not sure about something, it's always fine to ask questions to get you to a confident order for the thing you want.