I knew there was a reason why I took a CAD class every year of high school.
It's ALWAYS important to label every dimension on any plan you give to someone to create, whether it's a house or a bolt. Collin has the right idea on what they want you to provide them so that they can make you an accurate case. I would even suggest that you provide them with at least one side view as well. The more that you can provide them with, the happier they are. It allows them to perform a better job that will suit your expectations. Expecting a case that is 12 x 6 inches, for example, and receiving a case of that same size is much better than expecting a case of 'this size' x 'that size' and receiving something that is too short or too long.